In PHP, a function (or class method) could use variables that reside in the global scope by explicitly stating them with global keyword. For example:
$string = 'an apple above the head';
function break_string() {
global $string;
return 'break ' . $string;
}
This practice has some disadvantages, one of them is we can’t directly know the origin of the global variables. Let’s say we have this code:
include 'common_function.php';
include 'pedicure_function.php';
include 'medicure_function.php';
function break_string() {
global $string;
return 'break ' . $string;
}
Can you know where is the origin of global $string? We need to look through each of those included files and search for variable $string which resides in global scope. This might take some times, so I propose a better way to utilize global variables.
Let’s create one class as a container to all global variables by using static properties. To illustrate, see this piece of code:
// Global container
class G {
public static $string;
}
G::$string = 'an apple above the head';
function break_string() {
return 'break ' . G::$string;
}
Not only that we don’t need to write “global” in every functions, we could also find the origin of global $string easier, because it has G:: prefix. Finding the definition of a class is so much easier than finding a variable because people usually write one class per one file. Let’s take a look at this piece of code:
include 'class/G.php';
include 'common_function.php';
include 'header.inc';
function break_string() {
return 'break ' . G::$string;
}
In a glance, we could guess that G::$string originated from ‘class/G.php’ because we know for sure that G:: means static properties of class G and usually class G (or Whatever) will be written in file G.php (or Whatever.php).
