PHP variable scope and differ it from Javascript variable scope

Updated on ... 08th March 2023

In PHP and Javascript Variables have a limited "scope" which means that variable has a limited place where they are accessible. for example, if we defined $x=5; once somewhere in our application, it doesn't mean we can refer to $x from everywhere inside the application. $x has a limited scope within which it is valid and only code in the same scope has access to the variable.

The main difference b/w Javascript and PHP variable scope is observing their accessibility inside and outside of functions:

Javascript: Global variables are accessible inside the functions if defined outside of a function. There is an outer reference feature built into the engine that allows for variables in the outer environment to be visible and available in the execution context of a function.
To know more about Javascript variable scope and the differences between them click here

                                                
                                                
                                                //Global scope variable
var name = "Abdul";
function returnName(){
    //use variable inside of a function because name var is global scope
    console.log(name);

    //it returns Abdul
}

//use variable outside of a function because name var is global scope
console.log(name);
//it also  return Abdul

// call that function
returnName();

PHP: Global variables do not have scope inside functions (But we can use the ‘global‘ keyword for preceding the global variable inside the function to access them). Variables inside functions, conversely, do not have global scope and are not visible outside of their parent function (we can declare a variable inside a function as global by again using the keyword ‘global‘.)

                                                
                                                
                                                <?php
$name = 'Adbul'; // global scope

function myTest() {
// using $name inside this function will generate an error
echo "<p>Variable x inside function is: $name</p>";
}
myTest();

echo "<p>Variable x outside function is: <b> $name </b></p>";
?>

PHP Global variable with global keyword:

PHP has a global keyword to access the global scope variable inside the function

                                                
                                                
                                                <?php
$name = 'Adbul'; // global scope

function testFn() {
global $name;  // now $name can be access here
echo "<p>Variable x inside function is:<b> $name </b> </p>";
}
testFn();

echo "<p>Variable x outside function is: <b> $name </b></p>";
?>

Now we will discuss PHP variable scope:

The scope of a variable in the programming language is the part of the script in which place the variable can be referenced or used.

In PHP there are three types of variable scope:

global scope
local scope
static scope

Global scope

A variable declared outside of a function has a GLOBAL SCOPE and can only be accessed outside a function and we can also assess it inside the function using the global keyword as discussed above

                                                
                                                
                                                <?php
    $country = "india"; // global scope

    function testFn() {
    // using country inside this function will generate an error
    echo "<p>Variable x inside function is: $country</p>";
    }
    testFn();

    echo "<p>Variable x outside function is: $country</p>";
?>

Local scope

A variable declared within of a function has a LOCAL SCOPE and can only be accessed within that function:

                                                
                                                
                                                <?php

    function testFn() {
     $country = "india"; // local scope
     echo "<p>Variable x inside function is: $country</p>";
    }
    testFn();

    echo "<p>Variable x outside function is: $country</p>";
?>

Static scope

Generally, when a function is completed or executed, all of its variables are deleted. But, sometimes we would like a local variable NOT to be deleted. We need it for further operations.

for doing this, we use the static keyword when we first time declares the variable:

                                                
                                                
                                                <?php
    function testFn() {
    static $num = 10;
    echo $num;
    $num++;
    }

    testFn();
    testFn();
    testFn();
?>