PHP: How to validate a telephone number

This snippet is useful if you need to validate a telephone number using an editable list with specific formats.

<?php
/*
string validate_telephone_number (string $number, array $formats)
*/

function validate_telephone_number($number, $formats)
{
$format = trim(ereg_replace("[0-9]", "#", $number));

return (in_array($format, $formats)) ? true : false;
}

/* Usage Examples */

// List of possible formats: You can add new formats or modify the existing ones

$formats = array('###-###-####', '####-###-###',
				 '(###) ###-###', '####-####-####',
				 '##-###-####-####', '####-####', '###-###-###',
				 '#####-###-###', '##########');

$number = '08008-555-555';

if(validate_telephone_number($number, $formats))
{
echo $number.' is a valid phone number.';
}

echo "<br />";

$number = '123-555-555';

if(validate_telephone_number($number, $formats))
{
echo $number.' is a valid phone number.';
}

echo "<br />";

$number = '1800-1234-5678';

if(validate_telephone_number($number, $formats))
{
echo $number.' is a valid phone number.';
}

echo "<br />";

$number = '(800) 555-123';

if(validate_telephone_number($number, $formats))
{
echo $number.' is a valid phone number.';
}

echo "<br />";

$number = '1234567890';

if(validate_telephone_number($number, $formats))
{
echo $number.' is a valid phone number.';
}
?>