Its an alias of DateTimeZone::listIdentifiers()and returns numerically index array with all timezone identifiers
Example
<?php
$timezone_identifiers = timezone_identifiers_list();
for ($i=0; $i < 10; $i++)
echo $timezone_identifiers[$i].”<br />”;
?>
s
Output
Africa/Abidjan
Africa/Accra
Africa/Addis_Ababa
Africa/Algiers
Africa/Asmara
Africa/Bamako
Africa/Bangui
Africa/Banjul
Africa/Bissau
Africa/Blantyre