Require PHP files to only contain PHP (#24)

* Require PHP files to only contain PHP

* Update for PHP_CodeSniffer 3.4

* Don't need to upgrade

* Duplicate

* Changed my mind

Author: thewilkybarkid

src/Libero/ruleset.xml

@@ -11,8 +11,10 @@
     </rule>
 
     <rule ref="Generic.Arrays.DisallowLongArraySyntax"/>
+    <rule ref="Generic.Files.InlineHTML"/>
     <rule ref="Generic.Formatting.SpaceAfterCast"/>
     <rule ref="Generic.PHP.BacktickOperator"/>
+    <rule ref="Generic.PHP.CharacterBeforePHPOpeningTag"/>
     <rule ref="Generic.PHP.LowerCaseType"/>
     <rule ref="PEAR.WhiteSpace.ObjectOperatorIndent"/>
     <rule ref="SlevomatCodingStandard.Classes.ClassConstantVisibility">

tests/cases/php/bom

@@ -9,4 +9,7 @@ declare(strict_types=1);
 
 ---MESSAGES---
 1:1 Generic.Files.ByteOrderMark.Found
+---IGNORE-MESSAGES---
+1:1 Generic.Files.InlineHTML.Found
+1:2 Generic.PHP.CharacterBeforePHPOpeningTag.Found
 ---

tests/cases/php/closing-tag

@@ -1,5 +1,5 @@
 ---DESCRIPTION---
-No closing PHP tags at the end of files
+No closing PHP tags
 ---CONTENTS---
 <?php
 
@@ -9,11 +9,10 @@ $foo = 'bar';
 
 ?>
 
----FIXED---
 <?php
 
-declare(strict_types=1);
-
-$foo = 'bar';
+$baz = 'qux';
 
+---MESSAGES---
+8:1 Generic.Files.InlineHTML.Found
 ---

tests/cases/php/closing-tag-end

@@ -0,0 +1,19 @@
+---DESCRIPTION---
+No closing PHP tags at the end of files
+---CONTENTS---
+<?php
+
+declare(strict_types=1);
+
+$foo = 'bar';
+
+?>
+
+---FIXED---
+<?php
+
+declare(strict_types=1);
+
+$foo = 'bar';
+
+---

tests/cases/php/opening-tag

@@ -0,0 +1,11 @@
+---DESCRIPTION---
+No content before the opening PHP tag
+---CONTENTS---
+foo<?php
+
+declare(strict_types=1);
+
+---MESSAGES---
+1:1 Generic.Files.InlineHTML.Found
+1:4 Generic.PHP.CharacterBeforePHPOpeningTag.Found
+---

tests/cases/whitespace/opening-tag

@@ -0,0 +1,13 @@
+---DESCRIPTION---
+No whitespace before the opening PHP tag
+---CONTENTS---
+ <?php
+
+declare(strict_types=1);
+
+---FIXED---
+<?php
+
+declare(strict_types=1);
+
+---