PHP: testing for existence of a cell in a multidimensional array

Question

I have an array with numerous dimensions, and I want to test for the existence of a cell.

The below cascaded approach, will be for sure a safe way to do it:

if (array_key_exists($arr, 'dim1Key'))     if (array_key_exists($arr['dim1Key'], 'dim2Key'))       if (array_key_exists($arr['dim1Key']['dim2Key'], 'dim3Key'))         echo "cell exists";   

But is there a simpler way?

I'll go into more details about this:

1. Can I perform this check in one single statement?
2. Do I have to use array_key_exist or can I use something like isset? When do I use each and why?

Answer 1

isset() is the cannonical method of testing, even for multidimensional arrays. Unless you need to know exactly which dimension is missing, then something like

isset($arr[1][2][3]) 

is perfectly acceptable, even if the [1] and [2] elements aren't there (3 can't exist unless 1 and 2 are there).

However, if you have

$arr['a'] = null; 

then

isset($arr['a']); // false array_key_exists('a', $arr); // true 

comment followup:

Maybe this analogy will help. Think of a PHP variable (an actual variable, an array element, etc...) as a cardboard box:

• isset() looks inside the box and figures out if the box's contents can be typecast to something that's "not null". It doesn't care if the box exists or not - it only cares about the box's contents. If the box doesn't exist, then it obviously can't contain anything.
• array_key_exists() checks if the box itself exists or not. The contents of the box are irrelevant, it's checking for traces of cardboard.

Answer 2

I was having the same problem, except i needed it for some Drupal stuff. I also needed to check if objects contained items as well as arrays. Here's the code I made, its a recursive search that looks to see if objects contain the value as well as arrays. Thought someone might find it useful.

function recursiveIsset($variable, $checkArray, $i=0) {     $new_var = null;     if(is_array($variable) && array_key_exists($checkArray[$i], $variable))         $new_var = $variable[$checkArray[$i]];     else if(is_object($variable) && array_key_exists($checkArray[$i], $variable))         $new_var = $variable->$checkArray[$i];     if(!isset($new_var))         return false;      else if(count($checkArray) > $i + 1)         return recursiveIsset($new_var, $checkArray, $i+1);     else         return $new_var; } 

Use: For instance

recursiveIsset($variables, array('content', 'body', '#object', 'body', 'und')) 

In my case in drupal this ment for me that the following variable existed

$variables['content']['body']['#object']->body['und'] 

due note that just because '#object' is called object does not mean that it is. My recursive search also would return true if this location existed

$variables->content->body['#object']->body['und']