PHP Functions

A function is a self-contained block of code that can be called by your scripts. When called, the function’s code is executed and performs a particular task. You can pass values to a function, which then uses the values appropriately—storing them, transforming them, displaying them, whatever the function is told to do. When finished, a function can also pass a value back to the original code that called it into action.

PHP Built-in Functions

PHP has a lot of internal or built-in functions that you can call directly within your PHP scripts to perform a specific task, like echo(), print(), var_dump, etc.

PHP User-Defined Functions

In addition to the built-in functions, PHP also allows you to define your own functions. It is a way to create reusable code packages that perform specific tasks and can be kept and maintained separately form main program.

Advantages of using functions:

• Functions reduces the repetition of code within a program — Function allows you to extract commonly used block of code into a single component. Now you can perform the same task by calling this function wherever you want within your script without having to copy and paste the same block of code again and again.

• Functions makes the code much easier to maintain — Since a function created once can be used many times, so any changes made inside a function automatically implemented at all the places without touching the several files.

• Functions makes it easier to eliminate the errors — When the program is subdivided into functions, if any error occur you know exactly what function causing the error and where to find it. Therefore, fixing errors becomes much easier.

• Functions can be reused in other application — Because a function is separated from the rest of the script, it's easy to reuse the same function in other applications just by including the php file containing those functions.

Creating and Calling PHP Function

The basic syntax of creating a custom function can be give with:

function functionName(){
    // Code to be executed
} 

The declaration of a user-defined function start with the word function, followed by the name of the function you want to create followed by parentheses i.e. () and finally place your function's code between curly brackets {}.

function printhello()
 {
 echo "<h1>HELLO!</h1>";
 }

printhello();

PHP Functions with Parameters

PHP gives you option to pass your parameters inside a function. You can pass as many as parameters your like. These parameters work like variables inside your function. The following example takes two integer parameters and adds them together and then prints them.

<?php
function addFunction($num1, $num2)
{
$sum = $num1 + $num2;
echo "Sum of the two numbers is : $sum";
}
addFunction(10, 20);
?>

PHP Functions returning value

A function can return a value using the return statement in conjunction with a value or object. return stops the execution of the function and sends the value back to the calling code.

<?php
function addFunction($num1, $num2)
{
$sum = $num1 + $num2;
return $sum;
}
$return_value = addFunction(10, 20);
echo "Returned value from the function : $return_value";
?>