Calculate a timezone’s offset to UTC considering daylight savings time (e.g. CEST), print a string like “UTC+2” or “UTC-9”

calculate-utc-offset-dst.php

<?php
/**
 * Prints a string showing current time zone offset to UTC, considering daylight savings time.
 * @link                     http://php.net/manual/en/timezones.php
 * @param  string $time_zone Time zone name
 * @return string            Offset in hours, prepended by +/-
 */
function ch150918__utc_offset_dst( $time_zone = 'Europe/Berlin' ) {

	// Set UTC as default time zone.
	date_default_timezone_set( 'UTC' );
	$utc = new DateTime();

	// Calculate offset.
	$current   = timezone_open( $time_zone );
	$offset_s  = timezone_offset_get( $current, $utc ); // seconds
	$offset_h  = $offset_s / ( 60 * 60 ); // hours

	// Prepend “+” when positive
	$offset_h  = (string) $offset_h;
	if ( strpos( $offset_h, '-' ) === FALSE ) {
		$offset_h = '+' . $offset_h; // prepend +
	}

	return 'UTC' . $offset_h;
}

print-utc-offset-dst.php

<?php
/**
 * Will print “Berlin currently is UTC+2” during DST,
 * otherwise will print “Berlin currently is UTC+1”.
 *
 * Which is the truth, and nothing but the truth.
 */
$utc_offset = ch150918__utc_offset_dst();
printf( 'Berlin currently is %s', $utc_offset );