Formatting Phone Numbers in PHP

Assuming that your phone numbers always have this exact format, you can use this snippet:

$from = "+11234567890";
$to = sprintf("%s-%s-%s",
              substr($from, 2, 3),
              substr($from, 5, 3),
              substr($from, 8));

This function will format international (10+ digit), non-international (10 digit) or old school (7 digit) phone numbers. Any numbers other than 10+, 10 or 7 digits will remain unformatted.

function formatPhoneNumber($phoneNumber) {
    $phoneNumber = preg_replace('/[^0-9]/','',$phoneNumber);

    if(strlen($phoneNumber) > 10) {
        $countryCode = substr($phoneNumber, 0, strlen($phoneNumber)-10);
        $areaCode = substr($phoneNumber, -10, 3);
        $nextThree = substr($phoneNumber, -7, 3);
        $lastFour = substr($phoneNumber, -4, 4);

        $phoneNumber = '+'.$countryCode.' ('.$areaCode.') '.$nextThree.'-'.$lastFour;
    }
    else if(strlen($phoneNumber) == 10) {
        $areaCode = substr($phoneNumber, 0, 3);
        $nextThree = substr($phoneNumber, 3, 3);
        $lastFour = substr($phoneNumber, 6, 4);

        $phoneNumber = '('.$areaCode.') '.$nextThree.'-'.$lastFour;
    }
    else if(strlen($phoneNumber) == 7) {
        $nextThree = substr($phoneNumber, 0, 3);
        $lastFour = substr($phoneNumber, 3, 4);

        $phoneNumber = $nextThree.'-'.$lastFour;
    }

    return $phoneNumber;
}

$data = '+11234567890';

if(  preg_match( '/^\+\d(\d{3})(\d{3})(\d{4})$/', $data,  $matches ) )
{
    $result = $matches[1] . '-' .$matches[2] . '-' . $matches[3];
    return $result;
}

This is a US phone formatter that works on more versions of numbers than any of the current answers.

$numbers = explode("\n", '(111) 222-3333
((111) 222-3333
1112223333
111 222-3333
111-222-3333
(111)2223333
+11234567890
    1-8002353551
    123-456-7890   -Hello!
+1 - 1234567890 
');


foreach($numbers as $number)
{
    print preg_replace('~.*(\d{3})[^\d]{0,7}(\d{3})[^\d]{0,7}(\d{4}).*~', '($1) $2-$3', $number). "\n";
}

And here is a breakdown of the regex:

Cell: +1 999-(555 0001)

.*          zero or more of anything "Cell: +1 "
(\d{3})     three digits "999"
[^\d]{0,7}  zero or up to 7 of something not a digit "-("
(\d{3})     three digits "555"
[^\d]{0,7}  zero or up to 7 of something not a digit " "
(\d{4})     four digits "0001"
.*          zero or more of anything ")"

Updated: March 11, 2015 to use {0,7} instead of {,7}