Sure you are looking for the array_column function.

$newArray = array_column($originalArray,'0');

As said in PHP Manual, with this function you can extract, from an array of arrays, the only information you need. It is normally used with Associative arrays, but you can use a number as parameter and it will work as well.

In general, you can loop through a nested array the same way as you loop through a single-level array. Example:

$myArray = array(
    'first-level-first-key' => array(
        'second-level-first-key' => 'some value',
        'second-level-second-key' => 'another value'
    ),
    'first-level-second-key' => array(
        'seond-level-another-key' => 'yet another value'
    )
);

foreach($myArray as $first_level_key => $first_level_value) {
    echo 'Key: '. $first_level_key .'<br />';
    echo 'Values: ';
    foreach($first_level_value as $second_level_key => $second_level_value) {
        echo $second_level_value .', ';
    }
    echo '<br /><br />';
}

This will print out:

Key: first-level-first-key
Values: some value, another value,

Key: first-level-second-key
Values: yet another value,

Now you know how to loop through nested arrays. Have fun!

Edit

A little bit more explanation, as an answer to tmyie's comment below: As you can see every element is an array in itself:

$myArray['first-level-first-key'] = array('second-level-first-key' => ... );

The first foreach loops through all the 'first-level' arrays (in my example the elements with key 'first-level-....'). So within that loop, the variable $first_level_value holds an array. The second foreach loops through that, second-level, array. This nesting of loops is virtually endless if you have saved yet another array in that second level element.

Compare it with having a couple of boxes in front of you. With the first loop, you say 'Open up every box in front of me'. Then for every single box you have opened, the nested loop says 'Open up every box I found in that box', and so on.

Although there is most probably something very wrong with your application design if you'd write this, the following example is completely valid:

foreach($myArray as $x) {
    foreach(y) {
        foreach(z) {
            foreach(p) {
                // etc
            }
        }
    }
}

On PHP 5.5 or later, the simplest solution would be using PHP's built-in array_column() function.

$ids = array_column($arr, 'ID');

Since the response is in JSON, you would do something like the following:

$json = json_decode($result);
echo $json->result->success->contact->number;

Of course you should also add error handling, and check to see the object exists, etc.

For reference, I used the documentation outlining the response that is returned when sending a message as specified here: Send Message to Number

The response format (for success):

{
   "success":true,
   "result":{
      "success":[
         {
            "id":"308",
            "device_id":"4",
            "message":"hello world!",
            "status":"pending",
            "send_at":"1414624856",
            "queued_at":"0",
            "sent_at":"0",
            "delivered_at":"0",
            "expires_at":"1414634856",
            "canceled_at":"0",
            "failed_at":"0",
            "received_at":"0",
            "error":"None",
            "created_at":"1414624856",
            "contact":{
               "id":"14",
               "name":"Phyllis Turner",
               "number":"+447791064713"
            }
         }
      ],
      "fails":[

      ]
   }
}

Looks like you were able to figure it out from the comments and the other answer. However, I should clarify that my comments on the question were slightly misleading, so you can disregard them. I actually assumed class referred to PHP objects, when in fact class was simply a key for a string (the array looks to me like some parsed HTML/XML). I realized this when you posted a var_dump() of the array in the comments.

The issue is that the array structure is fairly complicated with all the nesting going on, so it may be difficult to see what's what. In general, I agree with the other answer; debugging with var_dump() is a great way to check. Here's my take on what the answer might be.

Assuming your array variable is $array:

1.

$array['query']['results']['div'][0]['span']['a']['href']
$array['query']['results']['div'][0]['span']['a']['img']['src']

2.

$array['query']['results']['div'][1]['span']['p']

3.

$array['query']['results']['span'][0]['content']

4.

$array['query']['results']['span'][1]['content']

In PHP >= 5.5 you can use array_column()

$letters = array_column($originalArray, 'id');

You can accomplice it by using array_search and array_column

This will give you the multidimensional array key

$key = array_search("JT", array_column($json['stock'], 'operator'));

Then you can do

$sims = $json['stock'][$key]['sims'];
print_r($sims) //this will print desired array

$user = $_SESSION['user'];
echo $user->id;

This seems to be what you need.