Check that a string matches a pattern in PHP (similar to the html5 pattern attribute). Useful for fallback server-side validation of textfield inputs when the textfield is validated client-side with the html5 pattern attribute.

string_matches_pattern.php

<?php

/**
 * HEADS UP! ---> turns out there is a better way to solve this problem.
 * Use ^ and $ to signify the beginning and end in your regex pattern and
 * then use preg_match(). It will get you the same result and faster! :)
 */

/**
 * Check that a string matches a pattern in PHP (similar to the html5 pattern
 * attribute).
 *
 * @param string $string
 *  The string to check against the pattern.
 * @param string $pattern
 *  A string containing a regular expression against which the string will be
 *  checked. For example, '/[a-zA-Z0-9]+/' is a whitelist pattern which only
 *  allows alphanumeric characters.
 * @return
 *  TRUE if $string only contains characters which match the pattern,
 *  otherwise FALSE.
 */
function string_matches_pattern($string, $pattern) {
  $matches = array();
  preg_match($pattern, $string, $matches);
  if (empty($matches) || (isset($matches[0]) && $matches[0] != $string)) {
    return FALSE;
  }
  return TRUE;
}

?>

Well, turns out this is entirely useless :). If you use ^ and $ to signify the beginning and end of your regex pattern then preg_match will give you the same result. so use preg_match!