A function for checking the syntax of PHP code.

php_lint.php

    /**
     * Check the syntax of a code snippet.
     *
     * @param $code
     *
     * @return mixed|null|string
     */
    function php_lint( $code )
    {
        $result = null;
        if ( ! function_exists('shell_exec') ) {
            return $result;
        }
        $temp     = tmpfile();
        $meta     = stream_get_meta_data($temp);
        $filename = $meta['uri'];
        fwrite($temp, "<?php $code");
        $result = shell_exec("php -n -l $filename");  // -n = no ini, -l = only lint
        fclose($temp);

        $result = trim($result);
        $result = str_replace("in $filename on", 'on', $result);
        $result = str_replace("\nErrors parsing $filename", '', $result);
        return $result;
    }