Restrict a phone number input field to accept only 6 8 and 10 digit numbers

Question

I have a phone number input field that looks like this:

<input type="text" name="phone" maxlength="10" size="40" value="{$tmp.phone}"><>

Can I apply a code inside here? Or would I apply a function in an external .php file to do this?

What would the code look like?

I am new to all this coding stuff and need some help...

Answer 1

You can use the new HTML5 attribute pattern . New browsers will not send the form until it is filled correct:

<form>
<input type="text" name="phone" pattern="^[0-9]{6}|[0-9]{8}|[0-9]{10}$" />
<input type="submit" />
</form>

If a user is using an older browser, the attribute is ignored. In this case you still should check it as Daniel and Pheonix recommended.

Answer 2

Even if get some way to put a check in HTML, always do validation on your server side. Client side Validations can always be by-passed.

in server side

$phone = $_GET['phone'];

if(!(strlen($phone)==6 ||strlen($phone)==8 ||strlen($phone)==10)){
  //Error
}

Answer 3

For better user experience you can validate using javascript, and for security reasons is mandatory to use server side validation as Pheonix said.

<form id="form_id">
<input id="phone_id" type="text" />
<input type="submit" 
    onclick="if (document.getElementById('phone_id').value.length != 6 
                 && document.getElementById('phone_id').value.length!=8 
                 && document.getElementById('phone_id').value.length!=10) 
                 { 
                     alert('Error message...'); 
                     return false; 
                 }" />
</form>