PHP function

In PHP, a function is a reusable block of code that performs a specific task. Functions help to organize code and make it easier to maintain and debug.

Creating a Function

The basic syntax for creating a function in PHP is:

function function_name() {
    // code to be executed
}

You can also define parameters in a function like this:

function function_name($parameter1, $parameter2) {
    // code to be executed
}

Calling a Function

Once a function is defined, you can call it anywhere in your code using its name:

function_name();

If the function requires parameters, you can pass them in when calling the function:

function_name($value1, $value2);

Returning a Value from a Function

Functions can return a value using the return statement. For example:

function sum($a, $b) {
    $result = $a + $b;
    return $result;
}

You can call this function and store the returned value in a variable:

$total = sum(5, 10);
echo $total; // Output: 15

You can also use the return statement to exit a function early:

function my_function($a, $b) {
    if ($a == $b) {
        return;
    }
    // code to be executed if $a is not equal to $b
}

In this example, the function exits early if the values of $a and $b are equal.

Passing Parameters by Reference

By default, parameters are passed to a function by value, which means that the function receives a copy of the parameter's value. If you want to modify the original parameter inside the function, you can pass it by reference using the & operator:

function my_function(&$parameter) {
    // code to modify $parameter
}

In this example, any changes made to $parameter inside the function will affect the original variable that was passed in.

Variable Scope

In PHP, variables have different levels of scope depending on where they are declared. Variables declared inside a function have local scope, which means they can only be accessed within the function. Variables declared outside of a function have global scope, which means they can be accessed anywhere in the script.

You can also use the global keyword to access a global variable from inside a function:

$global_variable = "Hello World!";

function my_function() {
    global $global_variable;
    echo $global_variable; // Output: Hello World!
}

In this example, the global keyword is used to access the $global_variable variable from inside the my_function() function.