PHP Global Variable

Updated April 13, 2023

Definition of PHP Global Variable

In any programming language, global variables are those variable which are declared outside the method or functions, also they can be declared inside of the functions as well. Global variable is just like any other variable but the difference is that this scope is global in application. If we make any variable global then we can access that variable from our whole application which means inside or outside of the script as well. Global variable functions the same way everywhere, as the name, suggests they are global for other resources. In the coming section, we will discuss more this PHP Global Variable in detail.

Syntax:

They can be declared like any other variable. But to access them we need to follow some standard. First, we will see how to declare a global variable in PHP which can be accessed anywhere in the application. See below;

$variable = your_value;

As you can see here we just need to define the variable name but for this, we use ‘$’ symbol. After this, we can assign any value to the variable we want. For better understanding, we will see one practice syntax which can be used in the program while coding;

e.g.:

$demoVar = "hello i am global variable";

How Global Variable work in PHP?

As now we know that global variables is declared globally to use anywhere in the application. This variable like any other variable in PHP. Also, these variables can be accessed from inside or outside of the function as well. As we have discussed earlier also that we just declare them like other variables, but in order to access them we need to follow some standard defined by the PHP. So here we will discuss how to use them inside the function and how to declare them. For better understanding, we will see one example for the beginners to get more clarity of the global variable. But before moving ahead we will discuss some of its property for accessing global variables we will also see where we store our global variable. In PHP, it maintains an array where it stores all the global variable that we defined in an application. By the use of this array, we can access this variable in and out of the script. Let’s discuss some important points for the global variable in order to use them inside the application see below;

1) Global Array

In PHP we use an array to access this global variable. Like any other programming language, it maintains the history of the global variable in an array. If we want to access any particular element or variable from the array then we have to pass the exact name of the variable in order to access them. Let’s see the syntax for this see below;

syntax:

$GLOBALS['variable_name']

As you can see in the above lines of code we are using ‘$GLOBALS’ keyword to access them followed by the square bracket. Inside this bracket, we have to give the variable name that we want to access. Let’s see one practice example for better understanding see below;

e.g. :

$GLOBALS['demovar']

2) Access them inside the function in PHP

IF we want to access the global variable inside any function or method then we can use the ‘global’ keyword. After mentioning the variable name with this we can use them throughout the function without the global keyword as well. For better understanding we will see one syntax to use them inside the function see below;

Syntax:

global $demovar1, $demovar2, $demovar3, $demovar4;
echo $demovar1;

As you can see in the above example that we are using a global keyword to access the variable inside the function. But once defined we are directly using them without the global keyword. Now we will look at some advantage of using a global variable in the application which is as follows;

Here are some points which needs to be taken into consideration while using the global keyword in PHP;

• IF you want to define a global variable you can use ‘$’ followed by the name of your variable.
• This variable can be accessed inside or outside of the functions well but to access them we have to ‘global’ keyword.
• We access the global variable inside nay thing by using the global array which maintains all the variables defined in the application.
• But keep in mind that the variable should be unique otherwise it will override like any other programming language.
• To access the variable directly from the array we have to use ‘$GLOBALS’ keyword followed by the variable name like we access an array by its index.
• The advantage of using a global variable is that we may require logged in user names everywhere in the application so by the use of it we can store them into the global variable and that can we easily accessed while application. Which will save memory and provide code optimization also.

Examples

In this example, we are declaring a global variables and trying to print and concatenate them. Simple program for beginners to start with a global variables in PHP.

Example #1

Code:

<!DOCTYPE html>
<html>
<body>
<h2 style = " color :red ">Demo on Global variable in PHP !!</h2>
<?php
//decraring global variable
$demovar1 = "Hello  ";
$demovar2 = "world  ";
$demovar3 = "demo  ";
$demovar4 = "global variable  ";
$demovar5 = "!!!";
//printing result here
echo $demovar1.$demovar2.$demovar3.$demovar4.$demovar5;
?>
</body>
</html>

Output:

Example #2

In this example, are trying to access the global variable from the function using an array.

Code:

<!DOCTYPE html>
<html>
<body>
<h2 style = " color :red ">Demo on Global variable in PHP !!</h2>
<?php
//decraring global variable
$demovar1= "Hello  ";
$demovar2 = "world  ";
$demovar3 = "demo  ";
$demovar4 = "global variable  ";
$demovar5 = "!!!";
// decralrig function
function demoFuntionForglobal() {
echo $GLOBALS['demovar1']."<br>";
echo $GLOBALS['demovar3']."<br>";
echo $GLOBALS['demovar4']."<br>";
echo $GLOBALS['demovar5']."<br>";
}
demoFuntionForglobal();
//printing result here
echo $demovar1.$demovar2.$demovar3.$demovar4.$demovar5;
?>
</body>
</html>

Output:

Conclusion

By using the global variable we can access variables in our whole application these are useful when we have to use same value in the whole application for example username, password and so many other details depend on the requirement. We just need to follow some standards while accessing them inside the function.

This is a guide to PHP Global Variable. Here we discuss the definition of PHP Global Variable, How Global Variable work in PHP along with the examples respectively. You may also have a look at the following articles to learn more –

1. PHP strlen()
2. PHP async
3. PHP array_pop()
4. PHP implode