called php functions from a namespace

Question

It seems I found a error when calling some php functions from a namespace that I can't understand it:

<?php
namespace test;
$var = "foo/bar";
echo 'let\'s call \strpos($var, \'o\'):', \strpos($var, 'o');
try{
 echo '<br />let\'s call \unset($var):';
 \unset($var);  //error!
 unset($var);  //correct!
 echo '<br />let\'s call \isset($var):';
 \isset($var);  //error!
 isset($var);  //correct!
}catch(\Exception $e){
 echo 'We have error:', $e->getMessage();
}
?>

Php says: Parse error: syntax error, unexpected T_UNSET, expecting T_STRING in global_namespace.php on line 7 Not even try...catch works and the error is reported ONLY for global functions isset() and unset()!

I fond it very bizarre, at least!

That's because namespaces aren't used for functions, they're used for classes. :) — Seer
– Seer, Commented Mar 14, 2013 at 20:04
Try/Catch doesn't work because what @Seer said. And: stackoverflow.com/questions/1900208/… — apelsinapa
– apelsinapa, Commented Mar 14, 2013 at 20:10
@Seer "Although any valid PHP code can be contained within a namespace, only four types of code are affected by namespaces: classes, interfaces, functions and constants." php.net/manual/en/language.namespaces.definition.php — deceze
– deceze ♦, Commented Mar 14, 2013 at 20:19

deceze · Accepted Answer · 2013-03-14 20:13:57Z

4

isset and unset aren't functions, they're language constructs. That means they're closer to operators like + and = than functions, hence do not play by the same rules. There's only one unset, you couldn't redefine it as a function if you wanted to.

Further, errors are not exceptions. You can't catch an error because it's not thrown. Even more so for syntax/parser errors, which happen before any code is even executed.

edited Mar 14, 2013 at 20:13

answered Mar 14, 2013 at 20:07

deceze♦

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4 Comments

centurian Over a year ago

Thanks 'deceze' for your answer: still find it very strange how these 'constructs' as you call them are implemented by the php team!

centurian Over a year ago

(Also, I just visited your project Kunststube-Router which I found very interesting as I'm trying to do the same for a project I'm working on-The Front Controller Pattern. Make a contact at your site so one can contact with!)

deceze Over a year ago

Language constructs are part of the language itself, not a pre-defined function. Think about it, a regular function cannot unset a variable. There's simply no mechanism for a regular function to do so. unset is defined by PHP as a reserved keyword and is handled by the PHP interpreter itself. Look through the PHP source code if you want to know the implementation details.

deceze Over a year ago

(And there are various contact details to be found in various places.)

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