A PHP function is a piece of code that can be reused many times. It can take input as an argument list and return value.

In PHP, we can define

• Conditional function
• Function within Function
• Recursive function

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 do not need to write the logic many times. By the use of the 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.
• Reducing duplication of code
• Decomposing complex problems into simpler pieces
• Improving the clarity of the code
• Information hiding

PHP User-defined Functions

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

Syntax

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

Note: The function name must start with a letter and underscore only like other labels in PHP. It can not start with numbers or special symbols.

PHP Functions Example

File Name: function_file.php

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

 Output: Hello PHP Function

PHP Function Arguments

We can pass the information in the PHP function through arguments that are separated by a comma.

PHP supports

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

Let us see the example to pass a single argument in the PHP function.

File Name: function_arg.php

<?php  
function myFunction($user_name){  
echo "Hello $user_name<br/>";  
}  
myFunction("Kamal");  
myFunction("Sonia");  
myFunction("Rani");  
?>  

Output:

Hello Kamal
Hello Sonia
Hello Rani

Let us see the example to pass two arguments in a PHP function.

File Name: function_args.php

<?php  
function getRecord($username,$age){  
echo "Hello $username, you are $age years old<br/>";  
}  
getRecord("Kamal",27);  
getRecord("Sonia",18);  
getRecord("Shivani",23);  
?>  

Output:

Hello Kamal, you are 27 years old
Hello Sonia, you are 18 years old
Hello Shivani, you are 23 years old

PHP Function: Default Argument Value

We can specify a default argument value in the function. While calling PHP function if you do not specify any argument, it will take the default argument. Let us see a simple example of using the default argument value in the PHP function.

Example of default Argument Value

PHP Function: Returning Value

Let us see an example of PHP function that returns a value.

File Name: function_defaultarg.php

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

Output: Cube of 3 is: 27