How to add elements to an empty array in PHP?

Question

If I define an array in PHP such as (I don\'t define its size):

$cart = array();

Do I simply add el

Answer 1

$cart = array();
$cart[] = 11;
$cart[] = 15;

// etc

//Above is correct. but below one is for further understanding

$cart = array();
for($i = 0; $i <= 5; $i++){
          $cart[] = $i;  

//if you write $cart = [$i]; you will only take last $i value as first element in array.

}
echo "
";
print_r($cart);
echo "
";