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Easy way to numeric representation of a quarter from passed as parametr date.

<?php
/**
 * quarterByDate()
 *
 * Return numeric representation of a quarter from passed free-form date.
 *
 * @param mixed $date
 * @return integer
 */
function quarterByDate($date)
{
    return (int)floor(date('m', strtotime($date)) / 3.1) + 1;
}
?>

Example:

<?php
$quarter = quarterByDate(date('Y-m-d'));    // current quarter. For 2009-08-29 will be "3"
$quarter = quarterByDate('2009-12');        // will be "4"
$quarter = quarterByDate('March');        // will be "1"
?>

I hope it will be useful.

Best regards,
S_P_E_C