PHP Functions

PHP function is a piece of code that can be reused many times. It can take input as argument list and return value. There are thousands of built-in functions in PHP.

In PHP, we can define Conditional function, Function within Function and Recursive function also.

Advantage of PHP Functions

Code Reusability: PHP functions are defined only once and can be invoked many times, like in other programming languages.

Less Code: It saves a lot of code because you don't need to write the logic many times. By the use of function, you can write the logic only once and reuse it.

Easy to understand: PHP functions separate the programming logic. So it is easier to understand the flow of the application because every logic is divided in the form of functions.

PHP User-defined Functions

We can declare and call user-defined functions easily. Let's see the syntax to declare user-defined functions.

Syntax

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

Note: Function name must be start with letter and underscore only like other labels in PHP. It can't be start with numbers or special symbols.

PHP Functions Example

<?php
function sayHello(){
echo "Hello PHP Function";
}
sayHello();//calling function
?>

Output:

PHP Function Arguments

We can pass the information in PHP function through arguments which is separated by comma.

PHP supports Call by Value (default), Call by Reference, Default argument values and Variable-length argument list.

Let's see the example to pass single argument in PHP function.

<?php
function sayHello($name){
echo "Hello $name
";
}
sayHello("Sonoo");
sayHello("Vimal");
sayHello("John");
?>

Output:

Hello Sonoo
Hello Vimal
Hello John

Let's see the example to pass two argument in PHP function.

<?php
function sayHello($name,$age){
echo "Hello $name, you are $age years old
";
}
sayHello("Sonoo",27);
sayHello("Vimal",29);
sayHello("John",23);
?>

Output:

Hello Sonoo, you are 27 years old
Hello Vimal, you are 29 years old
Hello John, you are 23 years old

PHP Call By Reference

Value passed to the function doesn't modify the actual value by default (call by value). But we can do so by passing value as a reference.

By default, value passed to the function is call by value. To pass value as a reference, you need to use ampersand (&) symbol before the argument name.

Let's see a simple example of call by reference in PHP.

Output:

Hello Call By Reference

PHP Function: Default Argument Value

We can specify a default argument value in function. While calling PHP function if you don't specify any argument, it will take the default argument. Let's see a simple example of using default argument value in PHP function.

<?php
function sayHello($name="Sonoo"){
echo "Hello $name
";
}
sayHello("Rajesh");
sayHello();//passing no value
sayHello("John");
?>

Output:

Hello Rajesh
Hello Sonoo
Hello John

PHP Function: Returning Value

Let's see an example of PHP function that returns value.

<?php
function cube($n){
return $n*$n*$n;
}
echo "Cube of 3 is: ".cube(3);
?>

Output:

Cube of 3 is: 27