preg_replace_callback Perform a regular expression search and replace using a callback mixedpreg_replace_callback mixedpattern mixedcallback mixedsubject intlimit The behavior of this function is almost identical to preg_replace, except for the fact that instead of replacement parameter, one should specify a callback that will be called and passed an array of matched elements in the subject string. The callback should return the replacement string. This function was added in PHP 4.0.5. See also preg_replace.