class FunctionDuplicateArgumentSniff

class FunctionDuplicateArgumentSniff implements Sniff {
    
    /**
     * Returns an array of tokens this test wants to listen for.
     *
     * @return array<int|string>
     */
    public function register() {
        return [
            T_FUNCTION,
        ];
    }
    
    //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 void
     */
    public function process(File $phpcsFile, $stackPtr) {
        $tokens = $phpcsFile->getTokens();
        $openBracket = $tokens[$stackPtr]['parenthesis_opener'];
        $closeBracket = $tokens[$stackPtr]['parenthesis_closer'];
        $foundVariables = [];
        for ($i = $openBracket + 1; $i < $closeBracket; $i++) {
            if ($tokens[$i]['code'] === T_VARIABLE) {
                $variable = $tokens[$i]['content'];
                if (in_array($variable, $foundVariables, true) === true) {
                    $error = 'Variable "%s" appears more than once in function declaration';
                    $data = [
                        $variable,
                    ];
                    $phpcsFile->addError($error, $i, 'Found', $data);
                }
                else {
                    $foundVariables[] = $variable;
                }
            }
        }
    }
    
    //end process()

}