Format ACF phone number in a text field

format-phone-number.php

<?
/*
  In this example our ACF field is 'footer_phone_number'
  *
  $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
  */

$original_phone = get_field('footer_phone_number', 'options-footer');
// Strip out all characters apart from numbers
$phone = preg_replace('/[^0-9]+/', '', $original_phone);
// Remove the 2 digit international code (+44)
if (substr($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;
?>
<div class="container">
	<div class="row">
		<div class="col footer-contact-links">
			<a class="footer-links-number" href="tel:<?= $phone; ?>"><?= $original_phone; ?></a>
		</div>
	</div>
</div>