You can see here some nice pics, it's exactly as you said.
http://schlueters.de/blog/archives/141-References-and-foreach.html
From: Tim Behrendsen t...@behrendsen.com
To: php-general@lists.php.net
Cc: Stephen stephe...@rogers.com; Matijn Woudt tijn...@gmail.com
Sent: Sunday, January 8, 2012 3:01 AM
Subject: Re: [PHP] Strange foreach reference issue
On 1/7/2012 4:44 PM, Stephen wrote:
On 12-01-07 07:30 PM, Tim Behrendsen wrote:
When you use an ampersand on the variable, that creates a reference to the
array elements, allowing you to potentially change the array elements
themselves (which I'm not doing here).
http://www.php.net/manual/en/control-structures.foreach.php
I do notice in the manual that it says, Reference of a $value and the last
array element remain even after the foreach loop. It is recommended to
destroy it by unset(). But that doesn't really explain why it contaminates
the next foreach loop in such an odd way. You would think that the $row in
the second loop would be assigned a non-reference value.
Tim
Tim,
You are using the $variable in an unintended (by PHP designers), and I
suggest undefined manner.
So the outcome cannot, but definition be explained.
Was this intended, and what were you trying to accomplish?
Stephen
In the real code, I just happen to use the same variable name first as a
reference, and then as a normal non-reference, and was getting the mysterious
duplicate rows.
I think I'm using everything in a completely reasonable way; the second foreach
is reassigning the loop variable. Nothing that comes before using that variable
ought to cause undefined behavior. The warning in the manual is about using the
loop variable as a reference after exiting the loop, but I'm not doing that.
I'm reassigning it, exactly as if I just decided to do a straight assignment of
$row
Ah ha, wait a minute, that's the key. OK, this is making more sense.
The first loop is leaving a reference to the final element. But then the second
foreach is doing a straight assignment to the $row variable, but $row is a
reference to the final element. So the foreach is assigning its iterated value
to the final element of the array, instead of a normal variable.
OK, I understand the logic now. The world now makes sense. The moral is always
unset the iterator variable when doing foreach with a reference, like the
manual says. :)
Thanks for everyone's help.
Tim
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