Calculate timezone offsets for PHP & WordPress

timezone.php

<?php

// This uses the wp option "gmt_offset" as "timezone_string" is not always defined

class Timezone
{
    public static function utc_offset()
    {
        return '+00:00';
    }

    // Will return an offset using the WordPress timezone set by the user
    // Example return values: -04:00, +00:00, or +5:45
    public static function local_offset()
    {
        // Start with the offset such as -4, 0, or 5.75
        $offset_number = (float) get_option('gmt_offset');

        // Build a string to represent the offset such as -04:00, +00:00, or +5:45
        $result = '';

        // Start with either - or +
        $result .= $offset_number < 0 ? '-' : '+';

        $whole_part = abs($offset_number);
        $hour_part = floor($whole_part);
        $minute_part = $whole_part - $hour_part;

        $hours = strval($hour_part);
        $minutes = strval($minute_part * 60);

        // Add hour part to result
        $result .= str_pad($hours, 2, '0', STR_PAD_LEFT);

        // Add separator
        $result .= ':';

        // Add minute part to result
        $result .= str_pad($minutes, 2, '0', STR_PAD_LEFT);

        return $result;
    }
}