php - What does backslash do as prefix to a function name? -

this question has answer here:

• reference — symbol mean in php? 15 answers

preparing zend-exam, found question class redefined strlen-function:

namespace myframework\mystring {   function strlen ($str)    {     return \strlen($str) * 2; // return double string-length   }  } 

i never came across "\function"-thing before , not explanation trainer - can pls. shed light...?

introduced in php 5.3, \ namespace separator.

in example, outer strlen myframework\mystring\strlen, inner strlen global one.

without namespace definition, class , function definitions placed global space - in php before namespaces supported. prefixing name \ specify name required global space in context of namespace.

reference: http://www.php.net/manual/en/language.namespaces.global.php