Mobile Phone Validation - Php

Apologies to bother you with a question that may seem quite blunt to some of you but I was wondering if any of you could shed some light on the validation side of things

Ive got a text field and I need validation on a mobile number so i need to validate that it has +44 at the beginning and including the +44 that it is 13 digits long , I found a few different techniques but nothing that defined it step by step only jus开发者_开发技巧t copy and paste , Id like to learn how to do it so I know for future reference.

Any help would be appreciated

Thanks

Although this can be done simply with PHP string functions, I would urge you take this opportunity to learn regular expressions. Once you are ready you can use PHP PCRE functions to apply that regular expression.

Note: This answer is intentionally generalized in the interest of teaching a man to fish, per the OP request. I encourage posting a separate, more specific question after reviewing these resources.

Easy way:

php code:

if (isset($_POST['send'])) {
    $mobile = $_POST['mobilenumber'];
    // get the first 3 string
    $begin = substr($mobile,0,3);
    // get the rest of the posted string and add it to 0 to make it to number
    // 'intval($variable)' and '(int) $variable' do the same
    $theOthers = 0+substr($mobile,3);
    // OR $theOthers = intval(substr($mobile,3));
    // OR $theOthers = (int) substr($mobile,3);
    $ok = true;
    echo strlen($mobile);
    // check the first 3 string
    // if it's not equal with "+44", the entry is wrong
    if ($begin != "+44") {
        $ok = false;
    } else {
        // check the length of the input
        // if it's not equal with 13, the entry is wrong
        if (strlen($mobile)!=13) {
            $ok = false;
        }
    }
    if ($ok) {
        // do something
    }   
}

html code:

<form method="post">
<input type="text" name="mobilenumber" maxlength="13" value="+44">
<input type="submit" name="send" value="Send">
</form>