class PregSecuritySniff

class PregSecuritySniff extends FunctionCall {
    
    /**
     * Returns an array of function names this test wants to listen for.
     *
     * @return array<string>
     */
    public function registerFunctionNames() {
        return [
            'preg_filter',
            'preg_grep',
            'preg_match',
            'preg_match_all',
            'preg_replace',
            'preg_replace_callback',
            'preg_split',
        ];
    }
    
    //end registerFunctionNames()
    
    /**
     * Processes this function call.
     *
     * @param \PHP_CodeSniffer\Files\File $phpcsFile    The file being scanned.
     * @param int                         $stackPtr     The position of the function call in
     *                                                  the stack.
     * @param int                         $openBracket  The position of the opening
     *                                                  parenthesis in the stack.
     * @param int                         $closeBracket The position of the closing
     *                                                  parenthesis in the stack.
     *
     * @return void
     */
    public function processFunctionCall(File $phpcsFile, $stackPtr, $openBracket, $closeBracket) {
        $tokens = $phpcsFile->getTokens();
        $argument = $this->getArgument(1);
        if ($argument === false) {
            return;
        }
        if ($tokens[$argument['start']]['code'] !== T_CONSTANT_ENCAPSED_STRING) {
            // Not a string literal.
            // @TODO: Extend code to recognize patterns in variables.
            return;
        }
        $pattern = $tokens[$argument['start']]['content'];
        $quote = substr($pattern, 0, 1);
        // Check that the pattern is a string.
        if ($quote === '"' || $quote === "'") {
            // Get the delimiter - first char after the enclosing quotes.
            $delimiter = preg_quote(substr($pattern, 1, 1), '/');
            // Check if there is the evil e flag.
            if (preg_match('/' . $delimiter . '[\\w]{0,}e[\\w]{0,}$/', substr($pattern, 0, -1)) === 1) {
                $warn = 'Using the e flag in %s is a possible security risk. For details see https://www.drupal.org/node/750148';
                $phpcsFile->addError($warn, $argument['start'], 'PregEFlag', [
                    $tokens[$stackPtr]['content'],
                ]);
                return;
            }
        }
    }
    
    //end processFunctionCall()

}