Trying to format phone number on keyin.

<?php // demo/validate_phone_numbers.php

/**
 * A function to validate a USA phone number and return a normalized string
 *
 * MAN PAGE: http://discuss.fogcreek.com/joelonsoftware3/default.asp?cmd=show&ixPost=102667&ixReplies=15
 * MAN PAGE: http://www.nanpa.com/number_resource_info/index.html
 */
error_reporting(E_ALL);


function strtophone($phone, $format=FALSE, $letters=FALSE, $dlm='-')
{
    if ($letters)
    {
        // TURN INPUT LIKE 1-800-BIG-DOGS
        // INTO INPUT LIKE 1-800-244-3647
        $phone = strtoupper($phone);
        if (preg_match('/[A-Z]/', $phone))
        {
            $phone = strtr
            ( $phone
            , 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
            , '22233344455566677778889999'
            )
            ;
        }
    }

    // DISCARD NON-NUMERIC CHARACTERS
    $phone = preg_replace('/[^0-9]/', NULL, $phone);

    // DISCARD A LEADING '1' FROM NUMBERS ENTERED LIKE 1-800-555-1212
    if (substr($phone,0,1) == '1') $phone = substr($phone,1);

    // IF LESS THAN TEN DIGITS, IT IS INVALID
    if (strlen($phone) < 10) return FALSE;

    // IF IT STARTS WITH '0' OR '1' IT IS INVALID, SECOND DIGIT CANNOT BE '9' (YET)
    if (substr($phone,0,1) == '0') return FALSE;
    if (substr($phone,0,1) == '1') return FALSE;
    if (substr($phone,1,1) == '9') return FALSE;

    // ISOLATE THE COMPONENTS OF THE PHONE NUMBER
    $ac = substr($phone,0,3); // AREA
    $ex = substr($phone,3,3); // EXCHANGE
    $nm = substr($phone,6,4); // NUMBER
    $xt = substr($phone,10);  // EXTENSION

    // ADD OTHER TESTS HERE AS MAY BE NEEDED - THESE ARE FOR LOCAL APPS
    if ($ac == '900') return FALSE;
    if ($ac == '976') return FALSE;
    if ($ex == '555') return FALSE;

    // IF NOT FORMATTED
    if (!$format) return $phone;

    // STANDARDIZE THE PRINTABLE FORMAT OF THE PHONE NUMBER LIKE 212-555-1212-1234
    $formatted_phone = $ac . $dlm . $ex . $dlm . $nm;
    if ($xt != '') $formatted_phone .= $dlm . $xt;
    return $formatted_phone;
}



// DEMONSTRATION OF THE FUNCTION IN ACTION.
if (!empty($_GET["p"]))
{
    // VALIDATE PHONE USING FUNCTION ABOVE
    if (!$phone = strtophone($_GET["p"], TRUE))
    {
        // FUNCTION RETURNS FALSE IF PHONE NUMBER IS UNUSABLE
        echo "BOGUS: {$_GET["p"]} ";
    }
    else
    {
        // SHOW THE FORMATTED PHONE
        echo "VALID: {$_GET["p"]} == $phone";
    }
}


// PUT UP A FORM TO TEST PHONE NUMBERS
function ph($p)
{
    echo "<br/><a href=\"{$_SERVER['PHP_SELF']}?p=" . urlencode($p) . "\">$p</a>" . PHP_EOL;
}

$form = <<<EOD
<form>
ENTER A PHONE NUMBER:
<input name="p" /><br/>
<input type="submit" />
</form>
TRY SOME OF THESE (CLICK OR COPY AND PASTE):
EOD;

echo $form;

ph('1-800-5551212');
ph('202-537-7560');
ph('202 537 7560');
ph('1-202-537-7560');
ph('(202) 537-7560');
ph('1.202.537.7560');
ph('123456789');
ph('703-356-5300 x2048');
ph('(212) 555-1212');
ph('1 + (212) 555-1212');
ph('1 (292) 226-7000');

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