PHP Functions

What is a Function?

A function is a reusable block of code that performs a specific task. Functions help organize your code, make it more readable, and allow you to avoid repetition.

Defining a Function

In PHP, you define a function using the function keyword, followed by the function name and parentheses.

<?php
function greet() {
    echo "Hello, World!";
}
?>

In this example, the function greet prints "Hello, World!" when called.

Calling a Function

To execute a function, simply call its name followed by parentheses:

<?php
greet(); // Outputs: Hello, World!
?>

Function Parameters

Functions can accept parameters, allowing you to pass values to them:

<?php
function greetUser($name) {
    echo "Hello, $name!";
}
greetUser("John"); // Outputs: Hello, John!
?>

Here, $name is a parameter that the function uses to personalize the greeting.

Returning Values

Functions can return values using the return statement:

<?php
function add($a, $b) {
    return $a + $b;
}
$result = add(5, 3); // $result now holds the value 8
?>

This function takes two parameters and returns their sum.

Default Parameters

You can set default values for function parameters:

<?php
function greet($name = "Guest") {
    echo "Hello, $name!";
}
greet(); // Outputs: Hello, Guest!
greet("Alice"); // Outputs: Hello, Alice!
?>

Variable-Length Argument Lists

You can use ...$args to accept a variable number of arguments:

<?php
function sum(...$numbers) {
    return array_sum($numbers);
}
echo sum(1, 2, 3, 4); // Outputs: 10
?>

This function calculates the sum of any number of arguments passed to it.

Anonymous Functions

PHP also supports anonymous functions (or closures), which are functions without a specified name:

<?php
$square = function($n) {
    return $n * $n;
};
echo $square(4); // Outputs: 16
?>

Conclusion

Functions are a powerful feature in PHP that enhance code reusability and organization. By understanding how to define, call, and manage functions, you can write cleaner and more efficient code.