Format UK Phone Number

format-phone.php

<?php

/*
    $original = '+44 (0)1234 567 890';
    $original = '0044 01234 567 890';
    $original = '01234 567 890';
    $original = '44 1234 567 890';

    Result should always be:
    '+441234567890
*/

// Strip out all characters apart from numbers
$phone = preg_replace('/[^0-9]+/', '', $original);

// Remove the 2 digit international code (+44)
if (substr($phone, 0, 2) == '44') {
	$phone = substr($phone, 2);
}

// Remove the 4 digit international code (0044)
if (substr($phone, 0, 4) == '0044') {
	$phone = substr($phone, 4);
}

// Remove the initial Zero from the number
// Some people write it in international numbers like this: +44 (0)1234 567 890
// But it shouldn't be entered when dialling
if (substr($phone, 0, 1) == '0') {
	$phone = substr($phone, 1);
}

// Add the international prefix
$phone = '+44' . $phone;

Thanks @lukearmstrong