array() + unset() = undefined offset

[gatzke]

Using the following code:

 

	$qwe = array('a','b','c','d','e');

for($i=0; $i<5; $i++)
{
	$asd = rand(0, sizeof($qwe)-1);
	echo $qwe[$asd];
	unset($qwe[$asd]);
}

 

gives the following error:

 

Notice: Undefined offset: <offset> in <directory>\<file>.php on line 7

[jcbones]

This is a simple problem.

 

You are recounting your array, on each loop.  So you will never get more than 3 returned values.

 

On top of this, you are removing the array keys, but you aren't re-ordering the keys.  So, at times your array keys would look like $qwe[0], $qwe[2], $qwe[4].

 

Now if the rand() function returned 3, you would get an un-defined index, because the key no longer exist in the array.

 

Simple fix, is to run it through array_values, to re-order the keys.

<?php

$qwe = array('a','b','c','d','e');

for($i=0; $i<sizeof($qwe); $i++) {
$asd = rand(0, sizeof($qwe)-1);
$qwe = array_values($qwe);
echo $qwe[$asd];
unset($qwe[$asd]);
}
?>

[Pikachu2000]

That makes sense. If it generates the same number twice, the index has already been unset and no longer exists, therefore throws a warning.

[gatzke]

Thank You jcbones, I just came here to answer myself! That's usually how it works for me; search for an answer for 3 hours, then post the question in a help forum, and finally find the solution while waiting for an answer.. 

[gatzke]

This is a simple problem.

 

You are recounting your array, on each loop.  So you will never get more than 3 returned values.

 

On top of this, you are removing the array keys, but you aren't re-ordering the keys.  So, at times your array keys would look like $qwe[0], $qwe[2], $qwe[4].

 

Now if the rand() function returned 3, you would get an un-defined index, because the key no longer exist in the array.

 

Simple fix, is to run it through array_values, to re-order the keys.

<?php

$qwe = array('a','b','c','d','e');

for($i=0; $i<sizeof($qwe); $i++) {
$asd = rand(0, sizeof($qwe)-1);
$qwe = array_values($qwe);
echo $qwe[$asd];
unset($qwe[$asd]);
}
?>

 

I just noticed you had started to answer my question before I edited my post. I changed

sizeof($qwe)

to "5" which also gave the error but was fixed by using your suggestion. Leaving

sizeof($qwe)

in tact results in only 3 letters being printed, so hard coding or copying the original size of $qwe into another variable does the trick:

$qwe = array('a','b','c','d','e');
$sizeofqwe = sizeof($qwe);

for($i=0; $i<$sizeofqwe; $i++) {...