Undefined index: why?

PHP
1

http://pastie.org/1386807

//Script works as it should but…

Notice: Undefined index on line 14

$machine = array();
foreach($brand_machines as $value) {
$machine[$value[‘list_type’]].= “<li><a href=\“find.php?name={$value[‘list’]}\”>{$value[‘name’]}</a></li>”;
}

i think it has to do with the part in bold… is there a better way to write that?

2

The bold is where your error is generated.
The error is generated when you request an item in the array, but that item identifier (index) does not exist.
From what I can gather about your script (the foreach) is that:

  • You are going through an array called $brand_machines.
  • You are not extracting the index and values of the array, only the values.
  • Each value in the array $brand_machines is also an array containing the following values:
  1. list_type
  2. list
  3. name
  • The $machine array is an empty array which should be populated by the foreach.

The part in bold basically first get the value of $value[‘list_type’] and then tries to find that as an index in $machines to add the value to.
What I would have done is at the line of: $machine = array();
is to rather use : $machine = array(‘the-first-list_type’ => ‘’ , ‘the-second-list_type’ => ‘’ , …);
Using this, you define the list_type index and then everything should be working. This will work as long as you know all the list_type(s) that can be used. There is however a more advanced way to dynamically add the index when it will be used, but I could not figure it out right now.

I hope this helps.
Jacotheron

3

the error message is telling you that $value[‘list_type’] does not exist.

4

$value[‘list_type’] does exist.

I’m creating an array with an dynamic key and appending values to it.

5

echo the value of $value[‘list_type’] just above your bolded line and post the value.

6

If a value is echoed like @Kalon suggested, try the following:
To be able to append values to a dynamic key, that key fist have to be created (dynamically or static).
Currently that key does not exist in the $machines array and you are trying to append to it.
Try adding the following before the bold part in the loop:

if(!isset($machines[$value['list_type']])){
    $machines[$value['list_type']] = '';
}

This will attempt to create the key in $machines when it does not exist. and then your code should be able to work.

7

It works. No notices thrown anymore:

foreach($brand_machines as $value) {
    if(!isset($machine[$value['list_type']])){
    $machine[$value['list_type']] = '';
}

    $machine[$value['list_type']] .= "<li><a href=\\"find.php?name={$value['list']}\\">{$value['name']}</a></li>";
}

So it throws the notice because that key doesn’t exist… it doesn’t exist so we create it here:

$machine[$value['list_type']] = ''

; <— but why isn’t the error thrown here? Is it the concatenation operator? It’s trying to attach something to something that doesn’t exist? If that is it, you have a sharp eye.

8

I like how a person from South Africa can help a guy out it America out at 5am… That’s collaboration, that’s why I love site point. I checked it out… it was the concatenation operator, Jacotheron. Looks like you were right too, Kalon. It was a single period that made the difference. Happy Holidays.

9

The $machines variable is empty in the first go. So accessing $machine[$value[‘list_type’]] will generate the warning every time a new $value[‘list_type’] is encountered. To avoid this warning, just initialize the variable before attempting to concatenate anything in it:

foreach($brand_machines as $value) {
	if(isset($machine[$value['list_type']])){
		$machine[$value['list_type']] = "";
	}
	$machine[$value['list_type']].= "<li><a href=\\"find.php?name={$value['list']}\\">{$value['name']}</a></li>";
}