(PHP 5 >= 5.3.0, PHP 7, PHP 8)
Without any namespace definition, all class and function definitions are placed into the global space - as it was in PHP before namespaces were supported. Prefixing a name with \
will specify that the name is required from the global space even in the context of the namespace.
Example #1 Using global space specification
<?php
namespace A\B\C;
function fopen() {
$f = \fopen(...); // call global fopen
return $f;
}
?>