Maximum length for a string for preg_replace() in PHP?

Question

I find that if I try to use preg_replace on a very long string, PHP returns an empty page to my browser without showing an error message. I was able to reproduce this bug in my testing environment. What is the maximum length of a string that preg_replace can handle? Is it possible to increase this length?

Answer 1

The same happened to me for $pattern matching string over 4M. Probably you will have to increase pcre.backtrack_limit using ini_set() or editing php.ini.

Check preg for last error:

    $retval = preg_replace ($pattern, $replacement, $subject);
    if ($retval === null) {
      // see http://php.net/manual/en/function.preg-last-error.php
      echo preg_last_error();
    }