一个验证函数

/**
* This function returns a regular expression pattern for commonly used expressions
* Use with / as delimiter for email mode and # for url modes
* mode can be: email|bbcode_htm|url|url_inline|www_url|www_url_inline|relative_url|relative_url_inline|ipv4|ipv6
*/
function get_preg_expression($mode)
{
  switch ($mode)
  {
    case 'email':
      return '(?:[a-z0-9\'\.\-_\+\|]++|&)+@[a-z0-9\-]+\.(?:[a-z0-9\-]+\.)*[a-z]+';
    break;

    case 'bbcode_htm':
      return array(
        '#<!\-\- e \-\-><a href="mailto:(.*?)">.*?</a><!\-\- e \-\->#',
        '#<!\-\- l \-\-><a (?:class="[\w-]+" )?href="(.*?)(?:(&|\?)sid=[0-9a-f]{32})?">.*?</a><!\-\- l \-\->#',
        '#<!\-\- ([mw]) \-\-><a (?:class="[\w-]+" )?href="(.*?)">.*?</a><!\-\- \1 \-\->#',
        '#<!\-\- s(.*?) \-\-><img src="\{SMILIES_PATH\}\/.*? \/><!\-\- s\1 \-\->#',
        '#<!\-\- .*? \-\->#s',
        '#<.*?>#s',
      );
    break;

    // Whoa these look impressive!
    // The code to generate the following two regular expressions which match valid IPv4/IPv6 addresses
    // can be found in the develop directory
    case 'ipv4':
      return '#^(?:(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])$#';
    break;

    case 'ipv6':
      return '#^(?:(?:(?:[\dA-F]{1,4}:){6}(?:[\dA-F]{1,4}:[\dA-F]{1,4}|(?:(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])))|(?:::(?:[\dA-F]{1,4}:){5}(?:[\dA-F]{1,4}:[\dA-F]{1,4}|(?:(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])))|(?:(?:[\dA-F]{1,4}:):(?:[\dA-F]{1,4}:){4}(?:[\dA-F]{1,4}:[\dA-F]{1,4}|(?:(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])))|(?:(?:[\dA-F]{1,4}:){1,2}:(?:[\dA-F]{1,4}:){3}(?:[\dA-F]{1,4}:[\dA-F]{1,4}|(?:(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])))|(?:(?:[\dA-F]{1,4}:){1,3}:(?:[\dA-F]{1,4}:){2}(?:[\dA-F]{1,4}:[\dA-F]{1,4}|(?:(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])))|(?:(?:[\dA-F]{1,4}:){1,4}:(?:[\dA-F]{1,4}:)(?:[\dA-F]{1,4}:[\dA-F]{1,4}|(?:(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])))|(?:(?:[\dA-F]{1,4}:){1,5}:(?:[\dA-F]{1,4}:[\dA-F]{1,4}|(?:(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.){3}(?:\d{1,2}|1\d\d|2[0-4]\d|25[0-5])))|(?:(?:[\dA-F]{1,4}:){1,6}:[\dA-F]{1,4})|(?:(?:[\dA-F]{1,4}:){1,7}:))$#i';
    break;

    case 'url':
    case 'url_inline':
      $inline = ($mode == 'url') ? ')' : '';
      $scheme = ($mode == 'url') ? '[a-z\d+\-.]' : '[a-z\d+]'; // avoid automatic parsing of "word" in "last word.http://..."
      // generated with regex generation file in the develop folder
      return "[a-z]$scheme*:/{2}(?:(?:[a-z0-9\-._~!$&'($inline*+,;=:@|]+|%[\dA-F]{2})+|[0-9.]+|\[[a-z0-9.]+:[a-z0-9.]+:[a-z0-9.:]+\])(?::\d*)?(?:/(?:[a-z0-9\-._~!$&'($inline*+,;=:@|]+|%[\dA-F]{2})*)*(?:\?(?:[a-z0-9\-._~!$&'($inline*+,;=:@/?|]+|%[\dA-F]{2})*)?(?:\#(?:[a-z0-9\-._~!$&'($inline*+,;=:@/?|]+|%[\dA-F]{2})*)?";
    break;

    case 'www_url':
    case 'www_url_inline':
      $inline = ($mode == 'www_url') ? ')' : '';
      return "www\.(?:[a-z0-9\-._~!$&'($inline*+,;=:@|]+|%[\dA-F]{2})+(?::\d*)?(?:/(?:[a-z0-9\-._~!$&'($inline*+,;=:@|]+|%[\dA-F]{2})*)*(?:\?(?:[a-z0-9\-._~!$&'($inline*+,;=:@/?|]+|%[\dA-F]{2})*)?(?:\#(?:[a-z0-9\-._~!$&'($inline*+,;=:@/?|]+|%[\dA-F]{2})*)?";
    break;

    case 'relative_url':
    case 'relative_url_inline':
      $inline = ($mode == 'relative_url') ? ')' : '';
      return "(?:[a-z0-9\-._~!$&'($inline*+,;=:@|]+|%[\dA-F]{2})*(?:/(?:[a-z0-9\-._~!$&'($inline*+,;=:@|]+|%[\dA-F]{2})*)*(?:\?(?:[a-z0-9\-._~!$&'($inline*+,;=:@/?|]+|%[\dA-F]{2})*)?(?:\#(?:[a-z0-9\-._~!$&'($inline*+,;=:@/?|]+|%[\dA-F]{2})*)?";
    break;
  }

  return '';
}