Format a local time/date using an ISO Format

date_iso.php

<?php

function date_iso($format, $timestamp = null)
{
	if ($timestamp === null) {
		$timestamp = time();
	}

	$convert = array(
		'a' => 'A' , 'B' => 'B', 'D' => 'z', 'ddd' => 't', 'dd' => 'd', 'd' => 'j',
		'EEEE' => 'l', 'EE' => 'D', 'eee' => 'N', 'e' => 'w', 'HH' => 'H', 'H' => 'G',
		'hh' => 'h', 'h' => 'g', 'I' => 'I', 'l' => 'L', 'MMMM' => 'F', 'MMM' => 'M',
		'MM' => 'm', 'M' => 'n', 'mm' => 'i', 'r' => 'r', 'SS' => 'S', 'ss' => 's',
		'U' => 'U', 'ww' => 'W', 'X' => 'Z', 'YYYY' => 'o', 'yyyy' => 'Y', 'yy' => 'y',
		'ZZZZ' => 'P', 'zzzz' => 'e', 'Z' => 'O', 'z' => 'T'
	);

	$values = preg_split(
		'/(a|B|D|d{1,3}|EEEE|EE|eee|e|HH|H|hh|h|I|l|M{1,4}|mm|r|SS|ss|U|ww|X|YYYY|yyyy|yy|ZZZZ|zzzz|Z|z|[^a-zA-Z]+)/',
		$format,
		-1,
		PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY
	);
	foreach ($values as $key => $value) {
		if (isset($convert[$value])) {
			$values[$key] = date($convert[$value], $timestamp);
		}
	}
	return implode($values);
}