Add sniff to check if file is executable

src/Standards/Generic/Docs/Files/FilePermissionsStandard.xml

@@ -0,0 +1,7 @@
+<documentation title="File Permissions">
+    <standard>
+    <![CDATA[
+    Files should not be executable.
+    ]]>
+    </standard>
+</documentation>

src/Standards/Generic/Sniffs/Files/FilePermissionsSniff.php

@@ -0,0 +1,53 @@
+<?php
+/**
+ * Tests that files are not executable.
+ *
+ * @author    Matthew Peveler <matt.peveler@gmail.com>
+ * @copyright 2019 Matthew Peveler
+ * @license   https://github.com/squizlabs/PHP_CodeSniffer/blob/master/licence.txt BSD Licence
+ */
+
+namespace PHP_CodeSniffer\Standards\Generic\Sniffs\Files;
+
+use PHP_CodeSniffer\Sniffs\Sniff;
+use PHP_CodeSniffer\Files\File;
+
+class FileExtensionSniff implements Sniff
+{
+    /**
+     * Returns an array of tokens this test wants to listen for.
+     *
+     * @return array
+     */
+    public function register()
+    {
+        return [T_OPEN_TAG];
+
+    }//end register()
+
+
+    /**
+     * Processes this test, when one of its tokens is encountered.
+     *
+     * @param \PHP_CodeSniffer\Files\File $phpcsFile The file being scanned.
+     * @param int                         $stackPtr  The position of the current token in the
+     *                                               stack passed in $tokens.
+     *
+     * @return int
+     */
+    public function process(File $phpcsFile, $stackPtr)
+    {
+        $perms = fileperms($phpcsFile->getFilename());
+
+        if ($perms & 0x0040 || $perms & 0x0008 || $perms & 0x0001) {
+            $error = "A PHP file must not be executable";
+            $phpcsFile->addError($error, $stackPtr, 'Executable');
+        }
+
+        // Ignore the rest of the file.
+        return ($phpcsFile->numTokens + 1);
+
+    }//end process()
+
+
+}//end class