The editor will teach you $GLOBALS in variables in PHP

This time we will no longer learn about delimiters in PHP. This article begins to introduce super global variables. Friends in need can refer to them. I hope everyone will become more and more familiar with PHP.

But before introducing $GLOBALS, let us first take a look at what super global variables are.

Global variable is one of the programming terms, which comes from the division of variables. Variables are divided into local variables and global variables. Local variables can also be called internal variables. Variables created by an object or function are usually local variables and can only be referenced internally and not by other objects or functions.

Global variables can be created by object functions or anywhere in this program. All objects or functions of this program can reference global variables. When a local variable is referenced by another object, it will have a null value. This does not happen with global variables.

Global variables are variables defined outside the function. Cannot be used directly in functions. Because its scope does not enter the function. PHP's predefined super global variables are available in all scopes of the script. It can be used in functions and classes without special instructions.

After knowing what super global variables are, let’s get down to business and take a look at $GLOBALS.

First look at a small example.

?php 
$x = 75;
$y = 25; 

function addition()
{
$GLOBALS['z'] = $GLOBALS['x'] + $GLOBALS['y'];
}

addition();
echo $z;
?>

The result is

100

Let’s look at the example. The result of z is x y, but he didn’t write it like the usual four arithmetic operations, but “$GLOBALS['x '] $GLOBALS['y']", what does this mean?

In fact, $GLOBALS is a global combined array containing all variables. The name of the variable is the key of the array, and we can access it in all scopes of the PHP script. As long as it is a global variable that has appeared, it can be obtained through the $GLOBALS array.

In the PHP life cycle, the so-called global variables defined outside the function body cannot be directly obtained inside the function.

The difference between global and $GLOBALS is:

global generates an alias variable in the function that points to the function's external variables, not the function's actual external variables.

$GLOBALS[] call is an external variable, and the internal and external functions are always consistent.

For member variables in a class, functions in the class must be accessed as $this-> instead of $GLOBALS:

global is used to define global variables , but this global variable does not apply to the entire website, but to the current page, including all files that include or require.

That’s all. If you want to know anything else, you can click here. → →php video tutorial

The above is the detailed content of The editor will teach you $GLOBALS in variables in PHP. For more information, please follow other related articles on the PHP Chinese website!