PHP - 使用PHP验证表单可以保证完整的验证，无论客户端使用什么浏览器？

Question

I have a relatively simple question.

Will using PHP guarantee that a form is always validated in the manner that was coded using PHP?

This being... If you do something like:

if (strlen($_POST['myInput'] == 0)
{
    Do this...
}

Will it apply no matter what client the user is making use of? E.g. IE, Firefox, Mobile Devices (Blackberry, Samsung), Linux Browsers?

The reason I ask this is because I fail to see the point in applying html validations like pattern at all.

Any input regarding this would be greatly appreciated. Thank you!

EDIT:

if (!preg_match("#^([0-9 ]{10,13})?$#", $_POST['myInput']))
{
    // Apply error pointers
    $_SESSION['myInputError'] = 'class="badInput" autofocus="autofocus"';

    include "$docRoot/html/forms/reg/user_info.html.php";
    exit();
}

Answer 1

The answer is yes, PHP is run by the server and not the client, therefor it will treat the input the same way always. So unless you make a specific code to make it act diffidently depending on the client's browser, it'll treat the input the same way.