diff --git a/.scrutinizer.yml b/.scrutinizer.yml
new file mode 100644
index 0000000..46b2435
--- /dev/null
+++ b/.scrutinizer.yml
@@ -0,0 +1,5 @@
+---
+checks:
+    php:
+        code_rating: true
+        duplication: true
diff --git a/.travis.yml b/.travis.yml
index c306e88..0f88d2a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,14 +7,23 @@ cache:
 
 sudo: false
 
-php:
-  - 5.5
+matrix:
+    include:
+        - php: 5.4
+        - php: 5.5
+        - php: 5.6
+        - php: 7.0
+        - php: 7.1
+
+
+before_install:
+    - phpenv config-rm xdebug.ini
+    - composer self-update -n
 
 before_script:
-  - composer self-update -n
-  - composer install -n --prefer-dist -v
-  - nohup php -S localhost:8080 -t features/fixtures/web > server.log 2>&1 &
+    - composer install -n --prefer-dist -v
+    - nohup php -S localhost:8080 -t features/fixtures/web > server.log 2>&1 &
 
 script:
-  - bin/phpcs --standard=PSR2 --encoding=UTF-8 --ignore="*.db,*.color,*.ttf" src/
-  - bin/behat --no-snippets --verbose --profile=travis -vvv
+    - bin/phpcs --standard=PSR2 --encoding=UTF-8 --ignore="*.db,*.color,*.ttf" src/
+    - bin/behat --no-snippets --verbose --profile=travis -vvv
diff --git a/composer.json b/composer.json
index 6a763fb..4b30990 100644
--- a/composer.json
+++ b/composer.json
@@ -22,16 +22,16 @@
         "files": ["src/Resources/data/constants.php"]
     },
     "require": {
-        "php": ">=5.5",
+        "php": ">=5.4",
         "ext-gd": "*"
     },
     "require-dev" : {
-        "behat/behat": "~3.0",
-        "behat/mink": "~1.7",
-        "behat/mink-goutte-driver": "~1.2",
-        "bossa/phpspec2-expect": "~1.0",
-        "sensiolabs/behat-page-object-extension": "~2.0@dev",
-        "squizlabs/php_codesniffer": "~2.3"
+        "behat/behat": "^3.3",
+        "behat/mink": "^1.7",
+        "behat/mink-goutte-driver": "^1.2",
+        "bossa/phpspec2-expect": "^1.0",
+        "sensiolabs/behat-page-object-extension": "^2.0",
+        "squizlabs/php_codesniffer": "^2.8"
     },
     "config": {
         "bin-dir": "bin"
diff --git a/src/Chart/BaseDraw.php b/src/Chart/BaseDraw.php
index 76c93b4..7674d96 100644
--- a/src/Chart/BaseDraw.php
+++ b/src/Chart/BaseDraw.php
@@ -295,8 +295,8 @@ public function allocateColor($Picture, $R, $G, $B, $Alpha = 100)
 
     /**
      * Convert apha to base 10
-     * @param int |float $AlphaValue
-     * @return int | float
+     * @param int|float $AlphaValue
+     * @return integer
      */
     public function convertAlpha($AlphaValue)
     {
@@ -502,9 +502,9 @@ public function processScale($XMin, $XMax, $MaxDivs, array $Factors, $AxisID)
 
     /**
      *
-     * @param int | float $Value1
-     * @param int | float $Value2
-     * @return int | float
+     * @param int|float $Value1
+     * @param int|float $Value2
+     * @return double
      */
     public function modulo($Value1, $Value2)
     {
@@ -527,8 +527,8 @@ public function modulo($Value1, $Value2)
     /**
      * @param mixed $Value
      * @param mixed $LastValue
-     * @param mixed $LabelingMethod
-     * @param mixed $ID
+     * @param integer $LabelingMethod
+     * @param integer $ID
      * @param boolean $LabelSkip
      * @return boolean
      */
@@ -574,23 +574,18 @@ public function countDrawableSeries()
      * @param int $Ya
      * @param int $Xb
      * @param int $Yb
-     * @return array
+     * @return integer[]
      */
     public function fixBoxCoordinates($Xa, $Ya, $Xb, $Yb)
     {
-        return array(
-            min($Xa, $Xb),
-            min($Ya, $Yb),
-            max($Xa, $Xb),
-            max($Ya, $Yb)
-        );
+        return array(min($Xa, $Xb), min($Ya, $Yb), max($Xa, $Xb), max($Ya, $Yb));
     }
 
     /**
      * Apply AALias correction to the rounded box boundaries
-     * @param int | float $Value
+     * @param int|float $Value
      * @param int $Mode
-     * @return int | float
+     * @return int|float
      */
     public function offsetCorrection($Value, $Mode)
     {
@@ -843,7 +838,7 @@ public function getRandomColor($Alpha = 100)
     /**
      * Validate a palette
      * @param mixed $Colors
-     * @param int | float $Surrounding
+     * @param int|float $Surrounding
      * @return array
      */
     public function validatePalette($Colors, $Surrounding = null)
@@ -913,7 +908,7 @@ public function validatePalette($Colors, $Surrounding = null)
      * @param mixed $Values
      * @param array $Option
      * @param boolean $ReturnOnly0Height
-     * @return array | int | float
+     * @return int|float|array
      */
     public function scaleComputeY($Values, array $Option = array(), $ReturnOnly0Height = false)
     {
@@ -1060,7 +1055,7 @@ public function scaleFormat($Value, $Mode = null, $Format = null, $Unit = null)
     }
 
     /**
-     * @return array | null
+     * @return array|null
      */
     public function scaleGetXSettings()
     {
@@ -1168,13 +1163,13 @@ public function writeBounds($Type = BOUND_BOTH, $Format = null)
 
                     if ($Type == BOUND_MAX || $Type == BOUND_BOTH) {
                         if ($MaxLabelPos == BOUND_LABEL_POS_TOP
-                            || ( $MaxLabelPos == BOUND_LABEL_POS_AUTO && $MaxValue >= 0)
+                            || ($MaxLabelPos == BOUND_LABEL_POS_AUTO && $MaxValue >= 0)
                         ) {
                             $YPos = $PosArray[$MaxPos] - $DisplayOffset + 2;
                             $Align = TEXT_ALIGN_BOTTOMMIDDLE;
                         }
                         if ($MaxLabelPos == BOUND_LABEL_POS_BOTTOM
-                            || ( $MaxLabelPos == BOUND_LABEL_POS_AUTO && $MaxValue < 0)
+                            || ($MaxLabelPos == BOUND_LABEL_POS_AUTO && $MaxValue < 0)
                         ) {
                             $YPos = $PosArray[$MaxPos] + $DisplayOffset + 2;
                             $Align = TEXT_ALIGN_TOPMIDDLE;
diff --git a/src/Chart/Bubble.php b/src/Chart/Bubble.php
index 7850387..7a1d56b 100644
--- a/src/Chart/Bubble.php
+++ b/src/Chart/Bubble.php
@@ -466,8 +466,7 @@ public function writeBubbleLabel($SerieName, $SerieWeightName, $Points, $Format
             } else {
                 $Description = "No description";
             }
-            $Series = "";
-            $Series[] = array("Format" => $Color, "Caption" => $Caption);
+            $Series = [["Format" => $Color, "Caption" => $Caption]];
 
             if ($Data["Orientation"] == SCALE_POS_LEFTRIGHT) {
                 if ($XDivs == 0) {
diff --git a/src/Chart/Cache.php b/src/Chart/Cache.php
index 16d7475..d95fb7a 100644
--- a/src/Chart/Cache.php
+++ b/src/Chart/Cache.php
@@ -361,7 +361,7 @@ public function saveFromCache($ID, $Destination)
     /**
      * Get file from cache
      * @param string $ID
-     * @return string | null
+     * @return string|null
      */
     public function getFromCache($ID)
     {
diff --git a/src/Chart/Data.php b/src/Chart/Data.php
index 5d60354..afa5330 100644
--- a/src/Chart/Data.php
+++ b/src/Chart/Data.php
@@ -179,7 +179,7 @@ public function reverseSerie($Series)
     /**
      * Return the sum of the serie values
      * @param string $Serie
-     * @return int | null
+     * @return int|null
      */
     public function getSum($Serie)
     {
@@ -233,7 +233,7 @@ public function setSerieShape($Series, $Shape = SERIE_SHAPE_FILLEDCIRCLE)
 
     /**
      * Set the description of a given serie
-     * @param mixed $Series
+     * @param string|array $Series
      * @param string $Description
      */
     public function setSerieDescription($Series, $Description = "My serie")
@@ -250,7 +250,7 @@ public function setSerieDescription($Series, $Description = "My serie")
 
     /**
      * Set a serie as "drawable" while calling a rendering public function
-     * @param mixed $Series
+     * @param string|array $Series
      * @param boolean $Drawable
      */
     public function setSerieDrawable($Series, $Drawable = true)
@@ -489,7 +489,7 @@ public function drawAll()
     /**
      * Return the average value of the given serie
      * @param string $Serie
-     * @return int | null
+     * @return int|null
      */
     public function getSerieAverage($Serie)
     {
@@ -497,13 +497,14 @@ public function getSerieAverage($Serie)
             $SerieData = $this->stripVOID($this->Data["Series"][$Serie]["Data"]);
             return array_sum($SerieData) / sizeof($SerieData);
         }
+
         return null;
     }
 
     /**
      * Return the geometric mean of the given serie
      * @param string $Serie
-     * @return int | null
+     * @return int|null
      */
     public function getGeometricMean($Serie)
     {
@@ -515,13 +516,14 @@ public function getGeometricMean($Serie)
             }
             return pow($Seriesum, 1 / sizeof($SerieData));
         }
+
         return null;
     }
 
     /**
      * Return the harmonic mean of the given serie
      * @param string $Serie
-     * @return int | null
+     * @return int|null
      */
     public function getHarmonicMean($Serie)
     {
@@ -540,7 +542,7 @@ public function getHarmonicMean($Serie)
     /**
      * Return the standard deviation of the given serie
      * @param string $Serie
-     * @return int | float | null
+     * @return double|null
      */
     public function getStandardDeviation($Serie)
     {
@@ -560,7 +562,7 @@ public function getStandardDeviation($Serie)
     /**
      * Return the Coefficient of variation of the given serie
      * @param string $Serie
-     * @return float | null
+     * @return float|null
      */
     public function getCoefficientOfVariation($Serie)
     {
@@ -578,7 +580,7 @@ public function getCoefficientOfVariation($Serie)
     /**
      * Return the median value of the given serie
      * @param string $Serie
-     * @return int | float
+     * @return int|float
      */
     public function getSerieMedian($Serie)
     {
@@ -598,7 +600,7 @@ public function getSerieMedian($Serie)
      * Return the x th percentil of the given serie
      * @param string $Serie
      * @param int $Percentil
-     * @return int | float | null
+     * @return int|float| null
      */
     public function getSeriePercentile($Serie = "Serie1", $Percentil = 95)
     {
@@ -645,7 +647,7 @@ public function addRandomValues($SerieName = "Serie1", array $Options = array())
 
     /**
      * Test if we have valid data
-     * @return boolean
+     * @return boolean|null
      */
     public function containsData()
     {
@@ -660,6 +662,8 @@ public function containsData()
                 return true;
             }
         }
+
+        return null;
     }
 
     /**
@@ -922,12 +926,12 @@ public function loadPalette($FileName, $Overwrite = false)
     /**
      * Initialise a given scatter serie
      * @param int $ID
-     * @return null | int
+     * @return null
      */
     public function initScatterSerie($ID)
     {
         if (isset($this->Data["ScatterSeries"][$ID])) {
-            return 0;
+            return null;
         }
 
         $this->Data["ScatterSeries"][$ID]["Description"] = "Scatter " . $ID;
@@ -1095,10 +1099,11 @@ public function importFromCSV($FileName, array $Options = array())
 
     /**
      * Create a dataset based on a formula
+     *
      * @param string $SerieName
      * @param string $Formula
      * @param array $Options
-     * @return null | int
+     * @return null
      */
     public function createFunctionSerie($SerieName, $Formula = "", array $Options = array())
     {
@@ -1110,11 +1115,11 @@ public function createFunctionSerie($SerieName, $Formula = "", array $Options =
         $AbscissaSerie = isset($Options["AbscissaSerie"]) ? $Options["AbscissaSerie"] : "Abscissa";
 
         if ($Formula == "") {
-            return 0;
+            return null;
         }
 
-        $Result = "";
-        $Abscissa = "";
+        $Result = [];
+        $Abscissa = [];
         for ($i = $MinX; $i <= $MaxX; $i = $i + $XStep) {
             $Expression = "\$return = '!'.(" . str_replace("z", $i, $Formula) . ");";
             if (@eval($Expression) === false) {
@@ -1188,7 +1193,8 @@ public function getData()
 
     /**
      * Save a palette element
-     * @param id $ID
+     *
+     * @param integer $ID
      * @param string $Color
      */
     public function savePalette($ID, $Color)
diff --git a/src/Chart/Draw.php b/src/Chart/Draw.php
index 5db0490..49e542a 100644
--- a/src/Chart/Draw.php
+++ b/src/Chart/Draw.php
@@ -126,9 +126,9 @@ public function drawPolygon(array $Points, array $Format = array())
      * @param int $Y1
      * @param int $X2
      * @param int $Y2
-     * @param int | float $Radius
+     * @param int|float $Radius
      * @param array $Format
-     * @return null | 0
+     * @return null|integer
      */
     public function drawRoundedRectangle($X1, $Y1, $X2, $Y2, $Radius, array $Format = array())
     {
@@ -192,9 +192,9 @@ public function drawRoundedRectangle($X1, $Y1, $X2, $Y2, $Radius, array $Format
      * @param int $Y1
      * @param int $X2
      * @param int $Y2
-     * @param int | float $Radius
+     * @param int|float $Radius
      * @param array $Format
-     * @return null | 0
+     * @return null|integer
      */
     public function drawRoundedFilledRectangle($X1, $Y1, $X2, $Y2, $Radius, array $Format = array())
     {
@@ -262,7 +262,7 @@ public function drawRoundedFilledRectangle($X1, $Y1, $X2, $Y2, $Radius, array $F
         $YBottom = $Y2 - $Radius;
 
         $Step = 360 / (2 * PI * $Radius);
-        $Positions = "";
+        $Positions = [];
         $Radius--;
         $MinY = null;
         $MaxY = null;
@@ -726,7 +726,7 @@ public function drawBezier($X1, $Y1, $X2, $Y2, $Xv1, $Yv1, $Xv2, $Yv2, array $Fo
 
             for ($j = 0; $j <= 3; $j++) {
                 if (!isset($Q[$ID])) {
-                    $Q[$ID] = "";
+                    $Q[$ID] = [];
                 }
                 if (!isset($Q[$ID]["X"])) {
                     $Q[$ID]["X"] = 0;
@@ -843,12 +843,12 @@ public function drawBezier($X1, $Y1, $X2, $Y2, $Xv1, $Yv1, $Xv2, $Yv2, array $Fo
 
     /**
      * Draw a line between two points
-     * @param int $X1
-     * @param int $Y1
-     * @param int $X2
-     * @param int $Y2
+     * @param int|float $X1
+     * @param int|float $Y1
+     * @param int|float $X2
+     * @param int|float $Y2
      * @param array $Format
-     * @return array | int
+     * @return array|int
      */
     public function drawLine($X1, $Y1, $X2, $Y2, array $Format = array())
     {
@@ -995,8 +995,8 @@ public function drawLine($X1, $Y1, $X2, $Y2, array $Format = array())
      * Draw a circle
      * @param int $Xc
      * @param int $Yc
-     * @param int | float $Height
-     * @param int | float $Width
+     * @param int|float $Height
+     * @param int|float $Width
      * @param array $Format
      */
     public function drawCircle($Xc, $Yc, $Height, $Width, array $Format = array())
@@ -1088,7 +1088,7 @@ public function drawCircle($Xc, $Yc, $Height, $Width, array $Format = array())
      * Draw a filled circle
      * @param int $X
      * @param int $Y
-     * @param int | float $Radius
+     * @param int|float $Radius
      * @param array $Format
      */
     public function drawFilledCircle($X, $Y, $Radius, array $Format = array())
@@ -1177,8 +1177,8 @@ public function drawFilledCircle($X, $Y, $Radius, array $Format = array())
 
     /**
      * Write text
-     * @param int $X
-     * @param int $Y
+     * @param int|float $X
+     * @param int|float $Y
      * @param string $Text
      * @param array $Format
      * @return array
@@ -1324,7 +1324,7 @@ public function drawText($X, $Y, $Text, array $Format = array())
      * @param int $Y2
      * @param int $Direction
      * @param array $Format
-     * @return null
+     * @return null|integer
      */
     public function drawGradientArea($X1, $Y1, $X2, $Y2, $Direction, array $Format = array())
     {
@@ -1440,7 +1440,7 @@ public function drawGradientArea($X1, $Y1, $X2, $Y2, $Direction, array $Format =
      * @param int $X
      * @param int $Y
      * @param array $Format
-     * @return int | null
+     * @return int|null
      */
     public function drawAntialiasPixel($X, $Y, array $Format = array())
     {
@@ -1527,7 +1527,7 @@ public function drawAntialiasPixel($X, $Y, array $Format = array())
      * @param int $R
      * @param int $G
      * @param int $B
-     * @return null
+     * @return null|integer
      */
     public function drawAlphaPixel($X, $Y, $Alpha, $R, $G, $B)
     {
@@ -1609,7 +1609,7 @@ public function drawFromJPG($X, $Y, $FileName)
      * @param string $FileName
      * @param int $X
      * @param int $Y
-     * @return null | 0
+     * @return null|integer
      */
     public function drawFromPicture($PicType, $FileName, $X, $Y)
     {
@@ -1949,7 +1949,7 @@ public function drawArrowLabel($X1, $Y1, $Text, array $Format = array())
      * Draw a progress bar filled with specified %
      * @param int $X
      * @param int $Y
-     * @param int | float $Percent
+     * @param int|float $Percent
      * @param array $Format
      */
     public function drawProgress($X, $Y, $Percent, array $Format = array())
@@ -2557,7 +2557,7 @@ public function drawScale(array $Format = array())
         $SkippedOuterTickWidth = isset($Format["SkippedOuterTickWidth"]) ? $Format["SkippedOuterTickWidth"] : 2;
 
         /* Floating scale require X & Y margins to be set manually */
-        if ($Floating && ( $XMargin == AUTO || $YMargin == 0 )) {
+        if ($Floating && ($XMargin == AUTO || $YMargin == 0)) {
             $Floating = false;
         }
 
@@ -4114,7 +4114,7 @@ public function drawScale(array $Format = array())
      * Draw an X threshold
      * @param mixed $Value
      * @param boolean $Format
-     * @return array | null | 0
+     * @return array|null|integer
      */
     public function drawXThreshold($Value, array $Format = array())
     {
@@ -4202,7 +4202,7 @@ public function drawXThreshold($Value, array $Format = array())
         }
 
         if ($Data["Orientation"] == SCALE_POS_LEFTRIGHT) {
-            $XStep = (($this->GraphAreaX2 - $this->GraphAreaX1) - $XScale[0] * 2 ) / $XScale[1];
+            $XStep = (($this->GraphAreaX2 - $this->GraphAreaX1) - $XScale[0] * 2) / $XScale[1];
             $XPos = $this->GraphAreaX1 + $XScale[0] + $XStep * $Value;
             $YPos1 = $this->GraphAreaY1 + $Data["YMargin"];
             $YPos2 = $this->GraphAreaY2 - $Data["YMargin"];
@@ -4268,7 +4268,7 @@ public function drawXThreshold($Value, array $Format = array())
                 return array("X" => $XPos);
             }
         } elseif ($Data["Orientation"] == SCALE_POS_TOPBOTTOM) {
-            $XStep = (($this->GraphAreaY2 - $this->GraphAreaY1) - $XScale[0] * 2 ) / $XScale[1];
+            $XStep = (($this->GraphAreaY2 - $this->GraphAreaY1) - $XScale[0] * 2) / $XScale[1];
             $XPos = $this->GraphAreaY1 + $XScale[0] + $XStep * $Value;
             $YPos1 = $this->GraphAreaX1 + $Data["YMargin"];
             $YPos2 = $this->GraphAreaX2 - $Data["YMargin"];
@@ -4342,7 +4342,7 @@ public function drawXThreshold($Value, array $Format = array())
      * @param mixed $Value1
      * @param mixed $Value2
      * @param array $Format
-     * @return array | null
+     * @return array|null
      */
     public function drawXThresholdArea($Value1, $Value2, array $Format = array())
     {
@@ -4377,7 +4377,7 @@ public function drawXThresholdArea($Value1, $Value2, array $Format = array())
         $XScale = $this->scaleGetXSettings();
 
         if ($Data["Orientation"] == SCALE_POS_LEFTRIGHT) {
-            $XStep = (($this->GraphAreaX2 - $this->GraphAreaX1) - $XScale[0] * 2 ) / $XScale[1];
+            $XStep = (($this->GraphAreaX2 - $this->GraphAreaX1) - $XScale[0] * 2) / $XScale[1];
             $XPos1 = $this->GraphAreaX1 + $XScale[0] + $XStep * $Value1;
             $XPos2 = $this->GraphAreaX1 + $XScale[0] + $XStep * $Value2;
             $YPos1 = $this->GraphAreaY1 + $Data["YMargin"];
@@ -4474,7 +4474,7 @@ public function drawXThresholdArea($Value1, $Value2, array $Format = array())
             $this->Shadow = $RestoreShadow;
             return array("X1" => $XPos1, "X2" => $XPos2);
         } elseif ($Data["Orientation"] == SCALE_POS_TOPBOTTOM) {
-            $XStep = (($this->GraphAreaY2 - $this->GraphAreaY1) - $XScale[0] * 2 ) / $XScale[1];
+            $XStep = (($this->GraphAreaY2 - $this->GraphAreaY1) - $XScale[0] * 2) / $XScale[1];
             $XPos1 = $this->GraphAreaY1 + $XScale[0] + $XStep * $Value1;
             $XPos2 = $this->GraphAreaY1 + $XScale[0] + $XStep * $Value2;
             $YPos1 = $this->GraphAreaX1 + $Data["YMargin"];
@@ -4562,7 +4562,7 @@ public function drawXThresholdArea($Value1, $Value2, array $Format = array())
      * Draw an Y threshold with the computed scale
      * @param mixed $Value
      * @param array $Format
-     * @return array | int
+     * @return array|int
      */
     public function drawThreshold($Value, array $Format = array())
     {
@@ -4783,7 +4783,7 @@ public function drawThreshold($Value, array $Format = array())
      * @param mixed $Value1
      * @param mixed $Value2
      * @param array $Format
-     * @return array | int | null
+     * @return array|int|null
      */
     public function drawThresholdArea($Value1, $Value2, array $Format = array())
     {
@@ -6122,7 +6122,7 @@ public function drawLineChart(array $Format = array())
      * @param string $SerieA
      * @param string $SerieB
      * @param array $Format
-     * @return null | 0
+     * @return null|integer
      */
     public function drawZoneChart($SerieA, $SerieB, array $Format = array())
     {
@@ -7077,7 +7077,7 @@ public function drawAreaChart(array $Format = array())
                     if ($this->Shadow) {
                         $ShadowArea = array();
                         foreach ($Areas as $Key => $Points) {
-                            $ShadowArea[$Key] = "";
+                            $ShadowArea[$Key] = [];
                             foreach ($Points as $Key2 => $Value) {
                                 if ($Key2 % 2 == 0) {
                                     $ShadowArea[$Key][] = $Value + $this->ShadowX;
@@ -7209,7 +7209,7 @@ public function drawAreaChart(array $Format = array())
                     if ($this->Shadow) {
                         $ShadowArea = array();
                         foreach ($Areas as $Key => $Points) {
-                            $ShadowArea[$Key] = "";
+                            $ShadowArea[$Key] = [];
                             foreach ($Points as $Key2 => $Value) {
                                 if ($Key2 % 2 == 0) {
                                     $ShadowArea[$Key][] = $Value + $this->ShadowX;
@@ -8148,7 +8148,7 @@ public function drawStackedBarChart(array $Format = array())
                             }
 
                             if (!isset($LastY[$Key])) {
-                                $LastY[$Key] = "";
+                                $LastY[$Key] = [];
                             }
                             if (!isset($LastY[$Key][$Pos])) {
                                 $LastY[$Key][$Pos] = $YZero;
@@ -8325,7 +8325,7 @@ public function drawStackedBarChart(array $Format = array())
                                 }
 
                                 if ($DisplayOrientation == ORIENTATION_VERTICAL
-                                    || ( $DisplayOrientation == ORIENTATION_AUTO && !$Done)
+                                    || ($DisplayOrientation == ORIENTATION_AUTO && !$Done)
                                 ) {
                                     if ($TxtHeight < $BarWidth && $TxtWidth < $BarHeight) {
                                         $this->drawText(
@@ -8386,7 +8386,7 @@ public function drawStackedBarChart(array $Format = array())
                             }
 
                             if (!isset($LastX[$Key])) {
-                                $LastX[$Key] = "";
+                                $LastX[$Key] = [];
                             }
                             if (!isset($LastX[$Key][$Pos])) {
                                 $LastX[$Key][$Pos] = $YZero;
@@ -8529,7 +8529,7 @@ public function drawStackedBarChart(array $Format = array())
                                 $TxtHeight = abs($TxtPos[2]["Y"] - $TxtPos[0]["Y"]);
                                 $TxtWidth = abs($TxtPos[1]["X"] - $TxtPos[0]["X"]);
 
-                                $XCenter = ( $X2 - $X1 ) / 2 + $X1;
+                                $XCenter = ($X2 - $X1) / 2 + $X1;
                                 $YCenter = (($Y + $YOffset + $YSize) - ($Y + $YOffset)) / 2 + $Y + $YOffset;
 
                                 $Done = false;
@@ -8560,7 +8560,7 @@ public function drawStackedBarChart(array $Format = array())
                                 }
 
                                 if ($DisplayOrientation == ORIENTATION_VERTICAL
-                                    || ( $DisplayOrientation == ORIENTATION_AUTO && !$Done)
+                                    || ($DisplayOrientation == ORIENTATION_AUTO && !$Done)
                                 ) {
                                     if ($TxtHeight < $BarWidth && $TxtWidth < $BarHeight) {
                                         $this->drawText(
@@ -8627,7 +8627,6 @@ public function drawStackedAreaChart(array $Format = array())
         $this->Shadow = false;
 
         /* Build the offset data series */
-        $OffsetData = "";
         $OverallOffset = "";
         $SerieOrder = "";
         foreach ($Data["Series"] as $SerieName => $Serie) {
@@ -9890,11 +9889,11 @@ public function drawLabelBox($X, $Y, $Title, array $Captions, array $Format = ar
      * @param int $R
      * @param int $G
      * @param int $B
-     * @param int | float $Alpha
+     * @param int|float $Alpha
      * @param int $BorderR
      * @param int $BorderG
      * @param int $BorderB
-     * @param int | float $BorderAlpha
+     * @param int|float $BorderAlpha
      */
     public function drawShape(
         $X,
@@ -10059,7 +10058,7 @@ public function drawShape(
      *
      * @param array $Points
      * @param array $Format
-     * @return null
+     * @return null|integer
      */
     public function drawPolygonChart(array $Points, array $Format = array())
     {
@@ -10180,9 +10179,9 @@ public function drawPolygonChart(array $Points, array $Format = array())
         $YStep = 1;
 
         if (!$NoFill) {
-            //if ( $DebugLine ) { $MinY = $DebugLine; $MaxY = $DebugLine; }
+            //if ($DebugLine ) { $MinY = $DebugLine; $MaxY = $DebugLine; }
             for ($Y = $MinY; $Y <= $MaxY; $Y = $Y + $YStep) {
-                $Intersections = "";
+                $Intersections = [];
                 $LastSlope = null;
                 $RestoreLast = "-";
                 foreach ($Segments as $Key => $Coords) {
@@ -10195,7 +10194,7 @@ public function drawPolygonChart(array $Points, array $Format = array())
                         if ($Y1 == $Y2) {
                             $X = $X1;
                         } else {
-                            $X = $X1 + (($Y - $Y1) * $X2 - ($Y - $Y1) * $X1 ) / ($Y2 - $Y1);
+                            $X = $X1 + (($Y - $Y1) * $X2 - ($Y - $Y1) * $X1) / ($Y2 - $Y1);
                         }
 
                         $X = floor($X);
@@ -10236,7 +10235,7 @@ public function drawPolygonChart(array $Points, array $Format = array())
                         if (is_array($Intersections)
                             && in_array($X, $Intersections)
                             && $LastSlope == "="
-                            && ($Slope == "-" )
+                            && ($Slope == "-")
                         ) {
                             $Intersections[] = $X;
                         }
diff --git a/src/Chart/Image.php b/src/Chart/Image.php
index 81f9b1a..46c96ea 100644
--- a/src/Chart/Image.php
+++ b/src/Chart/Image.php
@@ -89,7 +89,7 @@ public function setShadow($Enabled = true, array $Format = array())
      * @param int $Y1
      * @param int $X2
      * @param int $Y2
-     * @return int | null
+     * @return int|null
      */
     public function setGraphArea($X1, $Y1, $X2, $Y2)
     {
@@ -369,9 +369,10 @@ public function initialiseImageMap(
 
     /**
      * Add a zone to the image map
-     * @param mixed $Type
-     * @param mixed $Plots
-     * @param mixed $Color
+     *
+     * @param string $Type
+     * @param string $Plots
+     * @param string|null $Color
      * @param string $Title
      * @param string $Message
      * @param boolean $HTMLEncode
@@ -459,8 +460,8 @@ public function removeVOIDFromArray($SerieName, array $Values)
     /**
      * Replace the title of one image map serie
      * @param string $OldTitle
-     * @param string | array $NewTitle
-     * @return null | int
+     * @param string|array $NewTitle
+     * @return null|int
      */
     public function replaceImageMapTitle($OldTitle, $NewTitle)
     {
@@ -547,7 +548,7 @@ public function replaceImageMapTitle($OldTitle, $NewTitle)
      * Replace the values of the image map contents
      * @param string $Title
      * @param array $Values
-     * @return null | int
+     * @return null|int
      */
     public function replaceImageMapValues($Title, array $Values)
     {
diff --git a/src/Chart/Indicator.php b/src/Chart/Indicator.php
index aa7ab7b..0150235 100644
--- a/src/Chart/Indicator.php
+++ b/src/Chart/Indicator.php
@@ -32,12 +32,13 @@ public function __construct(Image $pChartObject)
 
     /**
      * Draw an indicator
+     *
      * @param int $X
      * @param int $Y
      * @param int $Width
      * @param int $Height
      * @param array $Format
-     * @return null | int
+     * @return null|int
      */
     public function draw($X, $Y, $Width, $Height, array $Format = array())
     {
@@ -105,7 +106,7 @@ public function draw($X, $Y, $Width, $Height, array $Format = array())
             $X2 = $X1 + ($Settings["End"] - $Settings["Start"]) * $XScale;
 
             if ($Key == 0 && $DrawLeftHead) {
-                $Poly = "";
+                $Poly = [];
                 $Poly[] = $X1 - 1;
                 $Poly[] = $Y;
                 $Poly[] = $X1 - 1;
diff --git a/src/Chart/Pie.php b/src/Chart/Pie.php
index 585c40c..f8671a8 100644
--- a/src/Chart/Pie.php
+++ b/src/Chart/Pie.php
@@ -15,7 +15,6 @@
  *
  *  You can find the whole class documentation on the pChart web site.
  */
-
 class Pie
 {
     /**
@@ -380,7 +379,7 @@ public function draw2DPie($X, $Y, array $Format = array())
                 }
 
                 if ($WriteValues == PIE_VALUE_PERCENTAGE) {
-                    $Display = round(( 100 / $SerieSum ) * $Value, $Precision) . "%";
+                    $Display = round((100 / $SerieSum) * $Value, $Precision) . "%";
                 } elseif ($WriteValues == PIE_VALUE_NATURAL) {
                     $Display = $Value . $ValueSuffix;
                 }
@@ -555,16 +554,16 @@ public function draw3DPie($X, $Y, array $Format = array())
                 $Xc = cos(($i - 90) * PI / 180) * $Radius + $X;
                 $Yc = sin(($i - 90) * PI / 180) * $Radius * $SkewFactor + $Y;
 
-                if (($SecondPass || $RestoreShadow ) && ( $i < 90 )) {
+                if (($SecondPass || $RestoreShadow) && ($i < 90)) {
                     $Yc++;
                 }
-                if (($SecondPass || $RestoreShadow ) && ( $i > 90 && $i < 180 )) {
+                if (($SecondPass || $RestoreShadow) && ($i > 90 && $i < 180)) {
                     $Xc++;
                 }
-                if (($SecondPass || $RestoreShadow ) && ( $i > 180 && $i < 270 )) {
+                if (($SecondPass || $RestoreShadow) && ($i > 180 && $i < 270)) {
                     $Xc++;
                 }
-                if (($SecondPass || $RestoreShadow ) && ( $i >= 270 )) {
+                if (($SecondPass || $RestoreShadow) && ($i >= 270)) {
                     $Xc++;
                     $Yc++;
                 }
@@ -580,7 +579,7 @@ public function draw3DPie($X, $Y, array $Format = array())
         }
 
         /* Draw the bottom shadow if needed */
-        if ($RestoreShadow && ($this->pChartObject->ShadowX != 0 || $this->pChartObject->ShadowY != 0 )) {
+        if ($RestoreShadow && ($this->pChartObject->ShadowX != 0 || $this->pChartObject->ShadowY != 0)) {
             foreach ($Slices as $SliceID => $Plots) {
                 $ShadowPie = array();
                 for ($i = 0; $i < count($Plots); $i = $i + 2) {
@@ -651,9 +650,9 @@ public function draw3DPie($X, $Y, array $Format = array())
         $SliceColors = array_reverse($SliceColors);
         foreach ($Slices as $SliceID => $Plots) {
             $Settings = $SliceColors[$SliceID];
-            $Settings["R"]+= 10;
-            $Settings["G"]+= 10;
-            $Settings["B"]+= 10;
+            $Settings["R"] += 10;
+            $Settings["G"] += 10;
+            $Settings["B"] += 10;
             $Settings["NoBorder"] = true;
             /* Empty error handling */
             if ($Visible[$SliceID]["Start"] && isset($Plots[2])) {
@@ -681,9 +680,9 @@ public function draw3DPie($X, $Y, array $Format = array())
         $SliceColors = array_reverse($SliceColors);
         foreach ($Slices as $SliceID => $Plots) {
             $Settings = $SliceColors[$SliceID];
-            $Settings["R"]+= 10;
-            $Settings["G"]+= 10;
-            $Settings["B"]+= 10;
+            $Settings["R"] += 10;
+            $Settings["G"] += 10;
+            $Settings["B"] += 10;
             $Settings["NoBorder"] = true;
             if ($Visible[$SliceID]["End"]) {
                 $this->pChartObject->drawLine(
@@ -710,9 +709,9 @@ public function draw3DPie($X, $Y, array $Format = array())
         /* Draw the rounded edges */
         foreach ($Slices as $SliceID => $Plots) {
             $Settings = $SliceColors[$SliceID];
-            $Settings["R"]+= 10;
-            $Settings["G"]+= 10;
-            $Settings["B"]+= 10;
+            $Settings["R"] += 10;
+            $Settings["G"] += 10;
+            $Settings["B"] += 10;
             $Settings["NoBorder"] = true;
 
             for ($j = 2; $j < count($Plots) - 2; $j = $j + 2) {
@@ -734,9 +733,9 @@ public function draw3DPie($X, $Y, array $Format = array())
             if ($SecondPass) {
                 $Settings = $SliceColors[$SliceID];
                 if (count($Border)) {
-                    $Settings["R"]+= 30;
-                    $Settings["G"]+= 30;
-                    $Settings["B"]+= 30;
+                    $Settings["R"] += 30;
+                    $Settings["G"] += 30;
+                    $Settings["B"] += 30;
                 }
 
                 /* Empty error handling */
@@ -779,9 +778,9 @@ public function draw3DPie($X, $Y, array $Format = array())
         /* Draw the top splice */
         foreach ($Slices as $SliceID => $Plots) {
             $Settings = $SliceColors[$SliceID];
-            $Settings["R"]+= 20;
-            $Settings["G"]+= 20;
-            $Settings["B"]+= 20;
+            $Settings["R"] += 20;
+            $Settings["G"] += 20;
+            $Settings["B"] += 20;
 
             $Top = array();
             for ($j = 0; $j < count($Plots); $j = $j + 2) {
@@ -906,7 +905,7 @@ public function draw3DPie($X, $Y, array $Format = array())
                 }
 
                 if ($WriteValues == PIE_VALUE_PERCENTAGE) {
-                    $Display = round(( 100 / $SerieSum ) * $Value, $Precision) . "%";
+                    $Display = round((100 / $SerieSum) * $Value, $Precision) . "%";
                 } elseif ($WriteValues == PIE_VALUE_NATURAL) {
                     $Display = $Value . $ValueSuffix;
                 }
@@ -1180,7 +1179,7 @@ public function setSliceColor($SliceID, array $Format = array())
      * @param int $X
      * @param int $Y
      * @param string $Label
-     * @param int | float $Angle
+     * @param int|float $Angle
      * @param array $Settings
      * @param boolean $Stacked
      * @param int $Xc
@@ -1302,7 +1301,7 @@ public function shift($StartAngle, $EndAngle, $Offset, $Reversed)
 
     /**
      * Internally used to write the re-computed labels
-     * @return null | int
+     * @return null|int
      */
     public function writeShiftedLabels()
     {
@@ -1643,7 +1642,7 @@ public function draw2DRing($X, $Y, array $Format = array())
                 }
 
                 if ($WriteValues == PIE_VALUE_PERCENTAGE) {
-                    $Display = round(( 100 / $SerieSum ) * $Value, $Precision) . "%";
+                    $Display = round((100 / $SerieSum) * $Value, $Precision) . "%";
                 } elseif ($WriteValues == PIE_VALUE_NATURAL) {
                     $Display = $Value . $ValueSuffix;
                 } else {
@@ -1996,7 +1995,7 @@ public function draw3DRing($X, $Y, array $Format = array())
                 if ($Angle == VOID) {
                     $Outer = false;
                     $Inner = true;
-                } elseif ($Inner && ($Angle < 90 || $Angle > 270 ) && isset($Plots["BottomPoly"][$ID * 2])) {
+                } elseif ($Inner && ($Angle < 90 || $Angle > 270) && isset($Plots["BottomPoly"][$ID * 2])) {
                     $Xo = $Plots["BottomPoly"][$ID * 2];
                     $Yo = $Plots["BottomPoly"][$ID * 2 + 1];
 
@@ -2112,7 +2111,7 @@ public function draw3DRing($X, $Y, array $Format = array())
                 if ($Angle == VOID) {
                     $Outer = false;
                     $Inner = true;
-                } elseif ($Outer && ($Angle > 90 && $Angle < 270 ) && isset($Plots["BottomPoly"][$ID * 2])) {
+                } elseif ($Outer && ($Angle > 90 && $Angle < 270) && isset($Plots["BottomPoly"][$ID * 2])) {
                     $Xo = $Plots["BottomPoly"][$ID * 2];
                     $Yo = $Plots["BottomPoly"][$ID * 2 + 1];
 
@@ -2209,7 +2208,7 @@ public function draw3DRing($X, $Y, array $Format = array())
 
                 $Label = "";
                 if ($WriteValues == PIE_VALUE_PERCENTAGE) {
-                    $Label = $Display = round(( 100 / $SerieSum ) * $Value, $Precision) . "%";
+                    $Label = $Display = round((100 / $SerieSum) * $Value, $Precision) . "%";
                 } elseif ($WriteValues == PIE_VALUE_NATURAL) {
                     $Label = $Data["Series"][$Data["Abscissa"]]["Data"][$Key];
                 }
diff --git a/src/Chart/Scatter.php b/src/Chart/Scatter.php
index dae439c..a65a456 100644
--- a/src/Chart/Scatter.php
+++ b/src/Chart/Scatter.php
@@ -42,7 +42,7 @@ public function __construct(Image $pChartObject, Data $pDataObject)
     /**
      * Prepare the scale
      * @param array $Format
-     * @return null | int
+     * @return null|int
      * @throws Exception
      */
     public function drawScatterScale(array $Format = array())
@@ -1735,7 +1735,7 @@ public function drawScatterBestFit(array $Format = array())
      * @param string $ScatterSerieID
      * @param mixed $Points
      * @param array $Format
-     * @return null | int
+     * @return null|int
      */
     public function writeScatterLabel($ScatterSerieID, $Points, array $Format = array())
     {
@@ -2037,8 +2037,8 @@ public function drawScatterThreshold($Value, array $Format = array())
 
     /**
      * Draw a Scatter threshold area
-     * @param int | float $Value1
-     * @param int | float $Value2
+     * @param int|float $Value1
+     * @param int|float $Value2
      * @param array $Format
      * @return type
      */
diff --git a/src/Chart/Split.php b/src/Chart/Split.php
index e48a65d..515b4cd 100644
--- a/src/Chart/Split.php
+++ b/src/Chart/Split.php
@@ -105,7 +105,6 @@ public function drawSplitPath(Image $Object, Data $Values, array $Format = array
                 "Surrounding" => $Surrounding
             );
 
-            $PolyGon = "";
 
             $Angle = $Object->getAngle($X2, $RightY1, $X1, $LeftY1);
             $VectorX1 = cos(deg2rad($Angle + 90)) * $Force + ($X2 - $X1) / 2 + $X1;
@@ -124,6 +123,8 @@ public function drawSplitPath(Image $Object, Data $Values, array $Format = array
                 $VectorY2,
                 $Settings
             );
+
+            $PolyGon = [];
             foreach ($Points as $Key => $Pos) {
                 $PolyGon[] = $Pos["X"];
                 $PolyGon[] = $Pos["Y"];
diff --git a/src/Chart/Spring.php b/src/Chart/Spring.php
index f963ddb..0998fa6 100644
--- a/src/Chart/Spring.php
+++ b/src/Chart/Spring.php
@@ -70,7 +70,7 @@ class Spring
     /**
      * @var boolean
      */
-    public $AutoComputeFreeZone= false;
+    public $AutoComputeFreeZone = false;
 
     public function __construct()
     {
@@ -168,7 +168,7 @@ public function autoFreeZone()
      * @param int $FromNode
      * @param int $ToNode
      * @param array $Settings
-     * @return null | int
+     * @return null|int
      */
     public function linkProperties($FromNode, $ToNode, array $Settings)
     {
@@ -262,7 +262,7 @@ public function setNodeDefaults(array $Settings = array())
      * Add a node
      * @param int $NodeID
      * @param array $Settings
-     * @return null | int
+     * @return null|int
      */
     public function addNode($NodeID, array $Settings = array())
     {
@@ -332,7 +332,7 @@ public function addNode($NodeID, array $Settings = array())
 
     /**
      * Set color attribute for a list of nodes
-     * @param array | string $Nodes
+     * @param array|string $Nodes
      * @param array $Settings
      */
     public function setNodesColor($Nodes, array $Settings = array())
@@ -415,9 +415,9 @@ public function dumpNodes()
 
     /**
      * Check if a connection exists and create it if required
-     * @param string | int $SourceID
-     * @param string | int $TargetID
-     * @return boolean | null
+     * @param string|int $SourceID
+     * @param string|int $TargetID
+     * @return boolean|null
      */
     public function checkConnection($SourceID, $TargetID)
     {
@@ -721,7 +721,7 @@ public function doPass()
     }
 
     /**
-     * @return int | float
+     * @return int|float
      */
     public function lastPass()
     {
@@ -790,7 +790,7 @@ public function lastPass()
                             $X4 = $Link["X2"];
                             $Y4 = $Link["Y2"];
 
-                            if (!($X1 == $X3 && $X2 == $X4 && $Y1 == $Y3 && $Y2 == $Y4 )) {
+                            if (!($X1 == $X3 && $X2 == $X4 && $Y1 == $Y3 && $Y2 == $Y4)) {
                                 if ($this->intersect($X1, $Y1, $X2, $Y2, $X3, $Y3, $X4, $Y4)) {
                                     if ($Link["Source"] != $Settings["Name"]
                                         && $Link["Source"] != $this->Data[$NodeID]["Name"]
@@ -1105,7 +1105,7 @@ public function drawSpring(Image $Object, array $Settings = array())
      * @param int $Y1
      * @param int $X2
      * @param int $Y2
-     * @return int | float
+     * @return int|float
      */
     public function getDistance($X1, $Y1, $X2, $Y2)
     {
@@ -1118,7 +1118,7 @@ public function getDistance($X1, $Y1, $X2, $Y2)
      * @param int $Y1
      * @param int $X2
      * @param int $Y2
-     * @return int | float
+     * @return int|float
      */
     public function getAngle($X1, $Y1, $X2, $Y2)
     {
diff --git a/src/Chart/Stock.php b/src/Chart/Stock.php
index 6c09e1b..880366b 100644
--- a/src/Chart/Stock.php
+++ b/src/Chart/Stock.php
@@ -40,7 +40,7 @@ public function __construct(Image $pChartObject, Data $pDataObject)
     /**
      * Draw a stock chart
      * @param array $Format
-     * @return type
+     * @return integer|null
      */
     public function drawStockChart(array $Format = array())
     {
diff --git a/src/Chart/Surface.php b/src/Chart/Surface.php
index 67097bc..db5d29f 100644
--- a/src/Chart/Surface.php
+++ b/src/Chart/Surface.php
@@ -66,7 +66,7 @@ public function setGrid($XSize = 10, $YSize = 10)
      * Add a point on the grid
      * @param int $X
      * @param int $Y
-     * @param int | float $Value
+     * @param int|float $Value
      * @param boolean $Force
      * @return null
      */
@@ -91,7 +91,7 @@ public function addPoint($X, $Y, $Value, $Force = true)
     /**
      * Write the X labels
      * @param array $Format
-     * @return null | int
+     * @return null|int
      */
     public function writeXLabels(array $Format = array())
     {
@@ -194,7 +194,7 @@ public function writeYLabels(array $Format = array())
 
     /**
      * Draw the area arround the specified Threshold
-     * @param int | float $Threshold
+     * @param int|float $Threshold
      * @param array $Format
      */
     public function drawContour($Threshold, array $Format = array())
@@ -344,7 +344,7 @@ public function drawSurface(array $Format = array())
      */
     public function computeMissing()
     {
-        $Missing = "";
+        $Missing = [];
         for ($X = 0; $X <= $this->GridSizeX; $X++) {
             for ($Y = 0; $Y <= $this->GridSizeY; $Y++) {
                 if ($this->Points[$X][$Y] == UNKNOWN) {
@@ -354,7 +354,7 @@ public function computeMissing()
         }
         shuffle($Missing);
 
-        foreach ($Missing as $Key => $Pos) {
+        foreach ($Missing as $Pos) {
             $Pos = preg_split("/,/", $Pos);
             $X = $Pos[0];
             $Y = $Pos[1];