Using namespaces: fallback to global function/constant
(PHP 5 >= 5.3.0, PHP 7)
Inside a namespace, when PHP encounters an unqualified Name in a class name, function or constant context, it resolves these with different priorities. Class names always resolve to the current namespace name. Thus to access internal or non-namespaced user classes, one must refer to them with their fully qualified Name as in:
Example #1 Accessing global classes inside a namespace
<?php
namespace?A\B\C;
class?Exception?extends?\Exception?{}
$a?=?new?Exception('hi');?//?$a?is?an?object?of?class?A\B\C\Exception
$b?=?new?\Exception('hi');?//?$b?is?an?object?of?class?Exception
$c?=?new?ArrayObject;?//?fatal?error,?class?A\B\C\ArrayObject?not?found
?>For functions and constants, PHP will fall back to global functions or constants if a namespaced function or constant does not exist.
Example #2 global functions/constants fallback inside a namespace
<?php
namespace?A\B\C;
const?E_ERROR?=?45;
function?strlen($str)
{
????return?\strlen($str)?-?1;
}
echo?E_ERROR,?"\n";?//?prints?"45"
echo?INI_ALL,?"\n";?//?prints?"7"?-?falls?back?to?global?INI_ALL
echo?strlen('hi'),?"\n";?//?prints?"1"
if?(is_array('hi'))?{?//?prints?"is?not?array"
????echo?"is?array\n";
}?else?{
????echo?"is?not?array\n";
}
?>Name resolution rules →
? 1997–2017 The PHP Documentation GroupLicensed under the Creative Commons Attribution License v3.0 or later.
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