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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