Check value to find if it was serialized

is_serialized.php

<?php 
/**
 * Check value to find if it was serialized.
 *
 * If $data is not an string, then returned value will always be false.
 * Serialized data is always a string.
 *
 * @param string $data   Value to check to see if was serialized.
 * @param bool   $strict Optional. Whether to be strict about the end of the string. Default true.
 * @return bool False if not serialized and true if it was.
 */
public function is_serialized($data,$strict = true) {
  // if it isn't a string, it isn't serialized.
  if (!is_string($data)) {
    return false;
  }
  $data = trim($data);
  if ('N;' == $data) {
    return true;
  }
  if (strlen($data)<4) {
    return false;
  }
  if (':'!== $data[1]) {
    return false;
  }
  if ($strict) {
      $lastc = substr( $data, -1 );
    if(';' !== $lastc &&'}' !== $lastc) {
      return false;
    }
  }else {
    $semicolon = strpos( $data, ';' );
    $brace     = strpos( $data, '}' );
    // Either ; or } must exist.
    if (false === $semicolon && false === $brace)
      return false;
    // But neither must be in the first X characters.
    if (false !== $semicolon && $semicolon < 3)
      return false;
    if (false !== $brace && $brace < 4)
      return false;
  }
  $token = $data[0];
  switch ($token) {
    case 's':
      if ($strict) {
        if ('"' !== substr( $data,-2,1)) {
          return false;
        }
      } elseif (false === strpos($data,'"')){
        return false;
      }
      // or else fall through
    case 'a':
    case 'O':
      return (bool) preg_match("/^{$token}:[0-9]+:/s", $data);
    case 'b':
    case 'i':
    case 'd':
      $end = $strict ? '$' : '';
      return (bool) preg_match("/^{$token}:[0-9.E-]+;$end/",$data);
  }
  return false;
}
?>