Telephone Number Format for href - Adapted from another source, unfortunately I don't recall where, let me know if you have seen this anywhere so I can credit.

PHP | Format UK telephone numbers for href

/*
	$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;