PHP not issuing any notice for undefined variable if the variable is passing to empty() or isset()

Question

<?php

function myFunction($yesNname) { } 

empty($noName);
print_r($noName);
isset($noName);

myFunction($noName);

output:

PHP Notice:  Undefined variable: noName ... on line 6 // print_r
PHP Notice:  Undefined variable: noName ... on line 9 // myFunction

The undefined variable is used in empty() and isset(). But PHP didn't issue notice about it. Why PHP shows discrimination to some function? How can I write such type of function?

What'd the point of having a function to test whether a variable exist, and make it trigger an error message when it doesn't exist? — Álvaro González
– Álvaro González, Commented Dec 14, 2012 at 10:52
@ÁlvaroG.Vicario I can understand that. I want to know how can I write such type of function. — Mohammed H
– Mohammed H, Commented Dec 14, 2012 at 10:55
Why would you want that? Could you please sketch out the situation? — giorgio
– giorgio, Commented Dec 14, 2012 at 10:58
@giorgio I thought there will be some technique in PHP to do that. — Mohammed H
– Mohammed H, Commented Dec 14, 2012 at 11:07

Álvaro González · Accepted Answer · 2012-12-14 11:26:38Z

3

Neither isset() nor empty() are functions. As the manual explains:

this is a language construct and not a function

To get this behaviour you'd need to tweak the PHP source code written in C.

It's possible that you can also get this behaviour with a PHP extension, but you'd also need to write it in C and install it in your server.

Update:

edited Dec 14, 2012 at 11:26

answered Dec 14, 2012 at 10:58

Álvaro González

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Comments

Mohammed H · Accepted Answer · 2012-12-14 11:20:33Z

3

Did you mean like:

if(!empty($noName)) {
 // print_r
 // function($noName);
}

edited Dec 14, 2012 at 11:20

Mohammed H

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answered Dec 14, 2012 at 10:57

Shlomo

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5 Comments

Mohammed H Over a year ago

Why should I put the condition for calling a function? did you see any such condition around the isset() or empty() in my code?

giorgio Over a year ago

Please note that isset is not needed in conjunction with empty (empty does already return false if a var does not exist)

giorgio Over a year ago

take it easy @habeebperwad, he's trying to help you... and is right actually

Mohammed H Over a year ago

@giorgio He tried to solve the PHP notice! He didn't tried to answer my question " How can I write such type of function?". Anyway, +1 for considering my question.

Sébastien Renauld Over a year ago

Someone already mentioned it: you can't. And why should you, anyway? The functions are already there, and atomic to boot. Why would you want to replicate something you can just use?

Valdars · Accepted Answer · 2012-12-14 11:30:23Z

2

There is no way to do it on function side. If you simply don't want to show errors you can either check variable first before calling function or use error control operator "@".

answered Dec 14, 2012 at 11:30

Valdars

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