How Can I Implement Stack in PHP?

Stack is a linear data structure which follows a particular order in which the operations are performed. The order is LIFO(Last In First Out). We can implement it in both procedural or object oriented approach. Here i follow the procedural approach.

$data_array = [];
$top = -1;

function push($top, $item, $data_array){
    global $top,$data_array;
    $top++;
    $data_array[$top] = $item;
    return $data_array;
}


function pop(){
    global $top,$data_array;
    if($top < 0)
        return -1;
    $top_item = $data_array[$top];
    unset($data_array[$top]);
    $top--;
    return $top_item;
}
push($top, 1, $data_array);
push($top, 2, $data_array);
push($top, 3, $data_array)

pop();