Variable scope determines where a variable can be accessed in a PHP program. Understanding scope helps you write organized functions and avoid unexpected variable behavior.
PHP variables can have different scopes. The main categories covered in this lesson are local, global, and static variables.
Example:
<?php
$name = "Rahul";
function showName() {
$student = "Amit";
echo $student;
}
showName();
echo "<br>";
echo $name;
?>Amit
Rahul
The variable $name is defined outside the
function, while $student is defined inside
it. Their scopes are different.
A variable declared inside a function normally has local scope. It can be accessed within that function, but not directly outside it.
<?php
function displayMessage() {
$message = "Welcome to PHP";
echo $message;
}
displayMessage();
?>Welcome to PHPExample of a local variable:
<?php
function calculateSum() {
$a = 10;
$b = 20;
echo $a + $b;
}
calculateSum();
?>30
The variables $a and $b
are local to calculateSum().
A local variable cannot normally be accessed directly outside the function in which it is declared.
<?php
function showAge() {
$age = 20;
echo $age;
}
showAge();
echo "<br>";
// This variable is not defined in the outer scope.
// echo $age;
?>20
The commented line is not executed. If you uncomment
it, PHP will report an undefined variable warning
because $age is not defined in the
outer scope.
To make a value available outside a function, you can return it and store the result in another variable.
<?php
function getAge() {
$age = 20;
return $age;
}
$studentAge = getAge();
echo $studentAge;
?>20A variable declared outside a function has global scope. It is not automatically available inside a function.
<?php
$course = "PHP";
function showCourse() {
// $course is not automatically available here.
echo "Learning programming";
}
showCourse();
echo "<br>";
echo $course;
?>Learning programming
PHP
The function can access the global variable only
through an appropriate method, such as the
global keyword or the
$GLOBALS array.
The global keyword allows a function
to access a variable from the global scope.
<?php
$number = 100;
function showNumber() {
global $number;
echo $number;
}
showNumber();
?>100Example: Modify a global variable
<?php
$count = 10;
function increaseCount() {
global $count;
$count = $count + 5;
}
increaseCount();
echo $count;
?>15
The function changes the global variable because
it declares global $count;.
Use global variables carefully because they create
dependencies between different parts of a program.
PHP provides the $GLOBALS superglobal
array for accessing global variables from different
parts of a script, including inside functions.
<?php
$price = 500;
function showPrice() {
echo $GLOBALS['price'];
}
showPrice();
?>500Example: Update a global variable
<?php
$total = 100;
function addAmount() {
$GLOBALS['total'] += 50;
}
addAmount();
echo $total;
?>150
The $GLOBALS array contains references
to variables in the global scope. The array keys
are the global variable names.
A local variable normally starts again when a
function is called. A variable declared with
static retains its value between
calls to that function.
<?php
function counter() {
static $count = 0;
$count++;
echo $count . "<br>";
}
counter();
counter();
counter();
?>1
2
3
The variable $count is local to the
function but retains its value between calls.
It is initialized only once for that function
execution context.
Without static:
<?php
function normalCounter() {
$count = 0;
$count++;
echo $count . "<br>";
}
normalCounter();
normalCounter();
normalCounter();
?>1
1
1Function parameters are local variables. They receive values when the function is called and can be used inside that function.
<?php
function calculateSquare($number) {
return $number * $number;
}
$result = calculateSquare(6);
echo $result;
?>36
The parameter $number belongs to
calculateSquare(). The variable
$result is defined in the outer scope.
Example: Separate local variables
<?php
function firstFunction() {
$message = "Hello";
echo $message . "<br>";
}
function secondFunction() {
$message = "Welcome";
echo $message;
}
firstFunction();
secondFunction();
?>Hello
Welcome
Both functions have a local variable named
$message. They do not share the same
local variable because each function has its own scope.
This example demonstrates local variables, function parameters, return values, and the use of separate functions without relying on global variables.
<?php
function calculateFee($monthlyFee, $months) {
$totalFee = $monthlyFee * $months;
return $totalFee;
}
function calculateBalance($totalFee, $paidFee) {
return $totalFee - $paidFee;
}
$studentName = "Rahul";
$monthlyFee = 1000;
$months = 6;
$paidFee = 4000;
$totalFee = calculateFee($monthlyFee, $months);
$balance = calculateBalance($totalFee, $paidFee);
echo "Student: " . $studentName . "<br>";
echo "Total Fee: Rs. " . $totalFee . "<br>";
echo "Paid Fee: Rs. " . $paidFee . "<br>";
echo "Pending Fee: Rs. " . $balance;
?>Student: Rahul
Total Fee: Rs. 6000
Paid Fee: Rs. 4000
Pending Fee: Rs. 2000The functions use their own local variables and receive information through parameters. Their return values are stored in variables outside the functions.
1. Where is a local variable normally accessible?
2. Which keyword allows a function to access a global variable?
3. What is the purpose of a static local variable?