PHP Manual

Global space

(PHP 5 >= 5.3.0, PHP 7)

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

namespace A\B\C;

/* This function is A\B\C\fopen */
function fopen() { 
/* ... */
$f = \fopen(...); // call global fopen
return $f;


PHP Manual