Improve code lisibility on field validation

Question

I receive an ad and I have to format the French phone number, which must not exceed 10 characters and contain only numbers. In case the criteria are not met I would like to return null.

I am not satisfied with my solution, would you have a simpler solution?

<?php

 function formatAds(array $ad): array
    {
        $ad['last_name'] = ucfirst($ad['last_name']);
        $ad['first_name'] = ucfirst($ad['first_name']);
        
        $phoneNumber  = str_replace(' ', '', $ad['phone_number']);
        $ad['phone_number']  = is_numeric($phoneNumber) && strlen($phoneNumber) === 10 ? $phoneNumber : null;
                       
        return $ad;
                   
    }
    
    
    $ad = [
            "last_name"    => "foo",
            "first_name"   => "bar",
            "phone_number" => "04 55 66 77 11",
        ];
        
    
    print_r(formatAds($ad));

You can see the code here: https://3v4l.org/PdTRG

Answer 1

Thanks CBroe , in accordance with what you said, I made these changes with a regex, it seems to work well even with the callsign, if you have other good ideas, I'm still interested.

<?php

 function formatAds(array $ad): array
    {
        $ad['last_name']     = ucfirst($ad['last_name']);
        $ad['first_name']    = ucfirst($ad['first_name']);
        
        $phoneNumber         = preg_replace(['/ /', '/^0?33/'], ['', '0'], $ad['phone_number']);
        $ad['phone_number']  = preg_match('/^0[1-9][\d]{8}$/', $phoneNumber, $matches) ? $matches[0] : null;
                       
        return $ad; 
                   
    }
    
    
    $ad = [
            "last_name"    => "foo",
            "first_name"   => "bar",
            "phone_number" => "04 55 66 77 11",
        ];
        
    $ad2 = [
            "last_name"    => "flow",
            "first_name"   => "blow",
            "phone_number" => "334 55 66 77 11",
        ];
        
    $ad3 = [
            "last_name"    => "beez",
            "first_name"   => "wiiz",
            "phone_number" => "0334 55 66 77 11",
        ];
        
    
    print_r(formatAds($ad));
    print_r(formatAds($ad2));
    print_r(formatAds($ad3));

Output:

Array
(
    [last_name] => Foo
    [first_name] => Bar
    [phone_number] => 0455667711
)
Array
(
    [last_name] => Flow
    [first_name] => Blow
    [phone_number] => 0455667711
)
Array
(
    [last_name] => Beez
    [first_name] => Wiiz
    [phone_number] => 0455667711
)

Code here: https://3v4l.org/PIX3X