What is function in PHP ?

The function is the block of statements which can be used repeatedly in the program and it will not execute when page is loaded , you need to call a function in order to execute them.

The real powers of the php comes with the functions.There are thousands of built-in functions in php .
Generally the functions are of two types.

1 . Built-in functions : The built-in function are those functions which comes with php itself , such as echo() , print() …

2 User Defined functions : The user defined functions are those functions which can be defined by the users themselves and can be re-used with in the programs .

Rules to declare a function : 

• First , It starts with the Access  Modifiers , such as public , private , protected etc 
• If there exist no Access  Modifiers it will be treated as the public .
• Secondly , Add the function name 
• The function name should start with either alphabet or underscore (_) , not a number or any special characters .
• With the curly bracket to start and end the bunch of codes . 
• Finally call the function to execute .

Note : To know more about PHP Access Modifiers click Here .

Syntax for user-defined functions : 

public function functionName() {
    #Block of code 
}

functionName() //calling the function 

Example : 

<?php
function php_function() {
    echo “Starting with the php functions !”;
}

php_function(); // call the function
?>

Output : 
Starting with the php functions !

PHP Function with Arguments : 

• The information is passed to the function via arguments , the the arguments are the values passed to in to the function to perform its operations .
• The arguments are just like a variables .
• The arguments are passed in to function inside the parentheses .
• The multiple arguments can be passed on to the function as comma separated , Ex : functionName( argument1 , argument2 , argument3 ,…….).
• Arguments assigned with equals to ( = ) are called the default arguments , if we don’t pass any argument to the function it will automatically the the default argument . 

Here , From the above example you can see the last function call doesn’t have the second argument and the default argument is assigned to it .

PHP Function with Returning values .

In order to return the value from the function you need to use “return” statement.

Let’s see the return statement from the above example :

<?php
function learn($course, $res=’Every thing’) {
    return “$course is $res . <br>”;
}

echo learn(“PHP”, “Interesting”);
echo learn(“Study”, “Boaring”);
echo learn(“Playing”, “good for health”);
echo learn(“Time”);

?>

Note : After returning the value , to print the output you need to print the statement with echo or print etc …