<?PHP
function _make_url_clickable_cb($matches) {
	$ret = '';
	$url = $matches[2];
 
	if ( empty($url) )
		return $matches[0];
	// removed trailing [.,;:] from URL
	if ( in_array(substr($url,-1),array('.',',';',':')) === true ) {
		$ret = substr($url,-1);
		$url = substr($url,strlen($url)-1);
	}
	return $matches[1] . "$url" . $ret;
}
 
function _make_web_ftp_clickable_cb($matches) {
	$ret = '';
	$dest = $matches[2];
	$dest = 'http://' . $dest;
 
	if ( empty($dest) )
		return $matches[0];
	// removed trailing [,;:] from URL
	if ( in_array(substr($dest,':')) === true ) {
		$ret = substr($dest,-1);
		$dest = substr($dest,strlen($dest)-1);
	}
	return $matches[1] . "$dest" . $ret;
}
 
function _make_email_clickable_cb($matches) {
	$email = $matches[2] . '@' . $matches[3];
	return $matches[1] . "$email";
}
 
function make_clickable($ret) {
	$ret = ' ' . $ret;
	// in testing,using arrays here was found to be faster
	$ret = preg_replace_callback('#([\s>])([\w]+?://[\w\\x80-\\xff\#$%&~/.\-;:=,?@\[\]+]*)#is','_make_url_clickable_cb',$ret);
	$ret = preg_replace_callback('#([\s>])((www|ftp)\.[\w\\x80-\\xff\#$%&~/.\-;:=,'_make_web_ftp_clickable_cb',$ret);
	$ret = preg_replace_callback('#([\s>])([.0-9a-z_+-]+)@(([0-9a-z-]+\.)+[0-9a-z]{2,})#i','_make_email_clickable_cb',$ret);
 
	// this one is not in an array because we need it to run last,for cleanup of accidental links within links
	$ret = preg_replace("#(]+?>|>))]+?>([^>]+?)#i","$1$3",$ret);
	$ret = trim($ret);
	return $ret;
}

/*** 以上代码来自：编程之家 jb51.cc（jb51.cc） ***/ 
?>