Create total element based value that have same value in array php

$containers = array_unique(array_column($data, 'CONTAINER'));
$count = count($containers);

1. array_column gets a column in a 2-dimensional array.
2. array_unique removes duplicates from the array.
3. count counts all the elements in the array.

You can use an array_map for that:

$yourArray = [
    ['x' => 'a', 'CONTAINER' => 'aa'],
    ['x' => 'a', 'CONTAINER' => 'bb'],
    ['x' => 'a', 'CONTAINER' => 'cc'],
    ['x' => 'a', 'CONTAINER' => 'aa'],
    ['x' => 'a', 'CONTAINER' => 'aa'],
    ['x' => 'a', 'CONTAINER' => 'bb'],
];


$arr = array_unique(array_map(function($x){ return $x['CONTAINER']; }, $yourArray));
echo (count($arr));

Itt will echos 3.

It's a bit unclear what you're asking - from what I understand, you wish to create an array with the CONTAINER values in this array.

You can do this by looping through the array and adding those values to a new array, like so:

//Set up new array
$containers = [];

//Loop through existing array
foreach($array as $a){

    //See if this array has a "container" key
    if($a["CONTAINER"]){

        //Push the new Container value to the $containers array
        $containers[] = $a["CONTAINER"];

    }

}

//Output the finished product
print_r($containers);

Once this is done, to count the number of elements with the CONTAINER key:

$num = count($containers);

For just the count of CONTAINER keys:

$n = 0;
foreach($array as $a){
    if($a["container"]) $n++;
}

echo $n;

To get all CONTAINER values do the following:

$key = 'CONTAINER';
$containers = array_map(function($item) use ($key) {
    return $item[$key];
}, $array);

print_r($containers);

If you just want to know how much CONTAINER values there are, do a count() after the above code.

echo count($containers);