PHP regular matching for strings

This article mainly introduces PHP's regular matching of strings. Interested friends can refer to it. I hope it will be helpful to everyone.

The specific implementation method is as follows:

/**
 * is_external_link 检测字符串是否包含外链
 * @param string $text 文字
 * @param string $host 域名
 * @return boolean    false 有外链 true 无外链
 * /
function all_external_link($text = '', $host = '') {
  if (empty($host)) $host = $_SERVER['HTTP_HOST'];
  $reg = '/http(?:s?):\/\/((?:[A-za-z0-9-]+\.)+[A-za-z]{2,4})/';
  preg_match_all($reg, $text, $data);
  $math = $data[1];
  foreach ($math as $value) {
    if($value != $host) return false;
  }
  return true;
}

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