Introduction

When writing PHP programs, you often need to perform the same task multiple times. Instead of writing the same code repeatedly, PHP provides Functions.

A function is a reusable block of code that performs a specific task whenever it is called.

• Easier to read
• Easier to maintain
• Reusable
• Faster to develop

What is a Function in PHP?

A function is a block of code that executes only when it is called.

Syntax

function functionName() {
    // Code
}

functionName();

Real-Life Example

Think of a function like a coffee machine. You press a button and it prepares coffee.

Press Button
      ↓
Coffee Machine Works
      ↓
Coffee Ready

Simple Function Example

<?php

function welcome()
{
    echo "Welcome to Learn PHP!";
}

welcome();

?>

Why Do We Need Functions?

Without Function

<?php

echo "Welcome Harsh";
echo "<br>";

echo "Welcome Amit";
echo "<br>";

echo "Welcome Rahul";

?>

With Function

<?php

function welcomeUser($name)
{
    echo "Welcome $name <br>";
}

welcomeUser("Harsh");
welcomeUser("Amit");
welcomeUser("Rahul");

?>

Types of Functions in PHP

1. Built-in Functions
2. User-Defined Functions

1. Built-in Functions

PHP already provides many ready-made functions.

strlen() Example

<?php

echo strlen("Harsh");

?>

strtoupper() Example

<?php

echo strtoupper("php");

?>

Popular Built-in Functions

2. User-Defined Functions

These are functions created by the programmer.

<?php

function greet()
{
    echo "Good Morning!";
}

greet();

?>

Function with Parameters

<?php

function student($name)
{
    echo "Hello $name";
}

student("Harsh");

?>

Multiple Parameters

<?php

function student($name, $course)
{
    echo "$name is studying $course";
}

student("Harsh", "PHP");

?>

Function with Return Value

<?php

function add($a, $b)
{
    return $a + $b;
}

$result = add(10, 20);

echo $result;

?>

Function with Default Parameter

<?php

function country($name = "India")
{
    echo $name;
}

country();
echo "<br>";
country("Japan");

?>

Square Function

<?php

function square($num)
{
    return $num * $num;
}

echo square(5);

?>

Real-Life Example: Online Shopping

<?php

function placeOrder($product)
{
    echo "$product ordered successfully!";
}

placeOrder("Laptop");

?>

Function Calling Another Function

<?php

function hello()
{
    echo "Hello ";
}

function user()
{
    hello();
    echo "Harsh";
}

user();

?>

Variable Scope

Local Variable

<?php

function demo()
{
    $x = 10;
    echo $x;
}

demo();

?>

Global Variable

<?php

$x = 100;

function demo()
{
    global $x;
    echo $x;
}

demo();

?>

Advantages of Functions

• Reduce duplicate code
• Improve readability
• Easy debugging
• Easy maintenance
• Reusable code
• Better organization

Common Interview Questions

1. What is a function in PHP?

A function is a reusable block of code that performs a specific task.

2. What are the two types of functions?

Built-in Functions and User-Defined Functions.

3. What is the difference between echo and return?

echo displays output directly.

return sends a value back to the caller.

Practice Questions

1. Create a function to print your name.
2. Create a function that adds two numbers.
3. Create a function that finds the largest of three numbers.
4. Create a function with a default country name.
5. Create a function that returns the square of a number.
6. Create a function that checks even or odd number.

Conclusion

Functions are one of the most important features in PHP because they allow developers to write clean, reusable, and maintainable code.