检查字符串中是否有外链

<?php
/**
* all_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;
}
?>