$re = '/^(((-?\d*(,\d+)?\*?)|\d+\/\d+)?(x(\^-?\d+)?)?)((\+|-)(((-?\d*(,\d+)?\*?)|\d+\/\d+)?(x(\^-?\d+)?)?))*$/';
$str = 'x^11-3x^9+12x^7+57/23x^6-6x^5+x^4-11*x^3+x^2-x-33
';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php