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Bug #74871 if statement behavior
Submitted: 2017-07-06 23:51 UTC Modified: 2017-07-07 00:04 UTC
From: johovich at yande dot ru Assigned:
Status: Not a bug Package: *General Issues
PHP Version: 7.1.7 OS: Linux version 2.6.32-531.23.3.lv
Private report: No CVE-ID: None
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 [2017-07-06 23:51 UTC] johovich at yande dot ru 
Description:
------------
If i use set var inside 'if' statement condition $var = '0' is the same as $var = false. But it is not the same. So if assign var to function that returns 0 as integer or 0 as string 'if' statement condition works as false.


Test script:
---------------
//In this script you can see, that set var value to 0 is equal to boolean false 
//applied to if statement. There is no diff between integer 0 or string '0'


if($pos = 0){
	$pos++;
} else {
	$pos = 0;
}
var_dump($pos);

//$pos is not boolean false, so it should do if condition true, but it's not

//to make this work well i use this
$pos = 0;
if($pos !== false){
	$pos++;
} else {
	$pos = 0;
}
var_dump($pos);

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 [2017-07-07 00:01 UTC] rtheunissen@php.net 
This is not a bug. `if ($condition)` is the same as `if ($condition == true)`, so in the second part of your test script if you changed the strict `!==` to `!=`, you would get the same results. 

So you're effectively saying `if (($pos = 0) == true)` which will drop to the `else`.
 [2017-07-07 00:04 UTC] rtheunissen@php.net
-Status: Open +Status: Not a bug
 [2017-07-07 00:04 UTC] rtheunissen@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

This is expected behaviour, an if statement defaults to a non-strict boolean comparison.
 [2017-07-07 08:52 UTC] spam2 at rhsoft dot net 
and "if($pos = 0)" is always true because = assigns a value while == and === compare a value

[harry@srv-rhsoft:/downloads]$ php test.php
DO NOT USE A SINGLE = TO COMPARE SOMETHING
[harry@srv-rhsoft:/downloads]$ cat test.php
<?php
if($test = 1)
{
 echo "DO NOT USE A SINGLE = TO COMPARE SOMETHING\n";
}
?>
 
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