Functions and Customizing Behavior in PHP

To create a function in PHP, use the function keyword, followed by the function name, a set of parentheses, and curly braces to define the function’s code block. Let’s create a simple function to greet users:

<?php
function greetUser() {
echo “Hello, User!”;
}

// Call the function
greetUser(); // Output: Hello, User!
?>

Functions can accept parameters (inputs) and return values (outputs), making them highly versatile. For example, let’s create a function to add two numbers and return the result:

<?php
function addNumbers($num1, $num2) {
return $num1 + $num2;
}

// Call the function
$result = addNumbers(5, 3);
echo $result; // Output: 8
?>

Variable scope refers to the accessibility of variables within different parts of the code. PHP has two main types of variable scope: global and local. Global variables can be accessed from anywhere in the script, while local variables are confined within a specific function. Here’s an example illustrating variable scope:

<?php
$globalVar = 10; // Global variable

function accessGlobal() {
global $globalVar;
echo $globalVar; // Output: 10
}

function modifyGlobal() {
global $globalVar;
$globalVar = 20;
}

accessGlobal();
modifyGlobal();
echo $globalVar; // Output: 20
?>

Anonymous functions, also known as closures, are functions without a name. They provide a way to create functions on-the-fly and are often used as callbacks in certain PHP functions. Here’s an example demonstrating the use of an anonymous function:

<?php
$greet = function ($name) {
echo “Hello, $name!”;
};

// Call the anonymous function
$greet(“John”); // Output: Hello, John!
?>

Recursion is a powerful technique where a function calls itself to solve a problem. It is commonly used in tasks with repetitive subtasks. A classic example is calculating the factorial of a number:

<?php
function factorial($n) {
if ($n === 1) {
return 1;
} else {
return $n * factorial($n – 1);
}
}

// Calculate factorial of 5
echo factorial(5); // Output: 120
?>