Two PHP functions to convert to convert to and from numbers compatible to MySQL's INET_ATON and INET_NTOA.

<?php

/**
 * Convert and IP address string to Long.
 *
 * Use these two functions to convert from and
 * to numbers compatible to MySQLs INET_ATON and INET_NTOA
 *
 * @link http://www.php.net/manual/en/function.long2ip.php#107257
 *
 * @param string $ip
 * @return int
 */
function convertIpToLong($ip)
{
    return sprintf("%u", ip2long($ip));
}

/**
 * Converts an IP address into it's string format representation.
 *
 * @param int $ip
 * @return string
 */
function convertIpToString($ip)
{
    $long = 4294967295 - ($ip - 1);

    return long2ip(- $long);
}

$ip4addressStr = '74.125.239.9';

echo "IP4 address String: $ip4addressStr\n";

$ip4addressLong = convertIpToLong($ip4addressStr);
echo "IP4 address String to Long: $ip4addressLong\n";

$ip4addressLong2Str = convertIpToString($ip4addressLong);
echo "IP4 address Long to String: $ip4addressLong2Str\n";