PHPで携帯電話番号の中の4桁を非表示にする方法

$num = "12345678910"
$str = substr_replace($num,'****',3,4);

<?php
$tel = &#39;12345678910&#39;;
//1.字符串截取法
$new_tel1 = substr($tel, 0, 3).&#39;****&#39;.substr($tel, 7);
var_dump($new_tel1);
//2.替换字符串的子串
$new_tel2 = substr_replace($tel, &#39;****&#39;, 3, 4);
var_dump($new_tel2);
//3.用正则
$new_tel3 = preg_replace(&#39;/(\d{3})\d{4}(\d{4})/&#39;, &#39;$1****$2&#39;, $tel);
var_dump($new_tel3);
?>

> string(11) "123****8910"
> string(11) "123****8910"
> string(11) "123****8910"