How do I define variables

$amount = 0 ; // value 0
$amount = $row['0']['amtpaid'] ; // by FETCH_ASSOC with lot of rows
$amount = $row['0'] ; // one field at index 0
$amount = $_POST ; // a full $_POST array in the var
$amount = $_GET['name'] ;// the field 'name' in $_GET
$amount = $_COOKIE['id'] ; the value for 'id' pick in the cookie
$amount; // discarding the value in, or init a var without value. Php is in C/C++ tail language

// as Php is very reliable with "T types" (int) and (double) are 'optional' on lot of servers. those are cast operator, converting Type to one another.

unset($amount) ; // free the var and its value, very good when big bunch of datas in a var, or object ( db / db result / curl ... )