$tel1 = "13888111188";
$tel2 = "+8613888111188";
$tel3 = "0861088111188";
$tel4 = "086-010-88111188";
echo preg_replace('/(^.*)\d{4}(\d{4})$/','\\1****\\2',$tel1),"\n";
echo preg_replace('/(^.*)\d{4}(\d{4})$/','\\1****\\2',$tel2),"\n";
echo preg_replace('/(^.*)\d{4}(\d{4})$/','\\1****\\2',$tel3),"\n";
echo preg_replace('/(^.*)\d{4}(\d{4})$/','\\1****\\2',$tel4),"\n";

------解决方案--------------------

PHP code

//屏蔽电话号码中间的四位数字
function hidtel($phone)
{
    $IsWhat = preg_match('/(0[0-9]{2,3}[\-]?[2-9][0-9]{6,7}[\-]?[0-9]?)/i',$phone); //固定电话
    if($IsWhat == 1)
    {
        return preg_replace('/(0[0-9]{2,3}[\-]?[2-9])[0-9]{3,4}([0-9]{3}[\-]?[0-9]?)/i','$1****$2',$phone);

    }
    else
    {
        return  preg_replace('/(1[358]{1}[0-9])[0-9]{4}([0-9]{4})/i','$1****$2',$phone);
    }
}