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PHP Functions

This PHP Functions tutorial helps you learn about the user-defined functions.

What are PHP Functions?

PHP Functions are a 'block of statements' which you can repeatedly use in a program to perform a specific task. A name is also given to this 'block of statements' so that you can call it by its name whenever you want to use it in your program/script.

There are thousands of built-in functions in PHP which you can directly use in your program/script.

Apart from built-in functions, user-defined functions are also supported by PHP, where you can define your own functions.

A function doesn't execute automatically on a page-load; a call to the function executes it.

PHP User Defined Functions

Let us see how to create your own functions in a program and use those functions.

<?php
function function_name() {
// function code statements
} ?>

Rules for the Functions

A function name can only have alphabets, numbers, and underscores. Special characters are not allowed.
The name of the function should either start with an alphabet or an underscore. The function name should not begin with a number.
Function names are not case-sensitive.
The start of the function code is marked by an opening curly brace { after the function name, and the end of the function code is marked by the closing curly brace }.

Example:

<?php
// defining the function
function greetings()
{
    echo "Welcome you on tutorialwithexample!";
}

echo "Hey Developers <br/>";
// calling the function
greetings();

// next line
echo "<br/>";

echo "Hey Nick <br/>";
// calling the function again
greetings();

?>

Output:

Hey Developers
Welcome you on developerstutorial!
Hey Nick
Welcome you on developerstutorial!

Advantages of User-defined Functions

Using PHP Functions for a large program can help you save time. Some of the advantages of using functions:

Reuseable Code: You have to write a function once, and you can repeatedly use it in your program.
Less Code Repetition: When there are multiple lines of code, rather than repeating all those lines of code repeatedly, you can create a function for them and call the function.
Easy to Understand: Using PHP functions in your program enables you to make the code more comprehensible and readable.

PHP Function Arguments

You can pass data to a function, which can be used inside the function block by using arguments. An argument is basically a variable.

You can specify arguments after the name of the function, in parentheses, separated by a comma. While defining a function, you must specify the number of arguments it will accept, and while calling the function, only that many arguments can be passed.

Syntax:

<?php
/* we can have as many arguments as we want to have in a function */
function function_name(argument1, argument2) {
// function code statements
}
?>

Example:

<?php
// defining the function with argument
function greetings($festival)
{
    echo "Wish you a very Happy $festival";
}

echo "Hey Jai <br/>";
// calling the function
greetings("Diwali");

// next line
echo "<br/>";

echo "Hey Jon <br/>";
// calling the function again
greetings("New Year");

?>

Output:

Hey Jai
Wish you a very Happy Diwali
Hey Jon
Wish you a very Happy New Year

As in the above-mentioned example, how the greetings() function was changed to start taking arguments, which can now be used to send greetings for different festivals.

PHP Default Function Arguments

Sometimes an important role is played by function arguments in the function code execution. In such cases, if an argument is not provided by the user while calling the function, it might lead to some error.

A user can provide a default value for the arguments to avoid such errors. This default value is used when no value is provided for the argument when the function is called.

Let's take an example.

<?php

// defining the function with default argument
function greetings($festival = "Life")
{
    echo "Wish you a very Happy $festival";
}

echo "Hey Jai <br/>";
// calling the function with an argument
greetings("Diwali");

// next line
echo "<br/>";

echo "Hey Jon <br/>";
// and without an argument
greetings();

?>

Output:

Hey Jai
Wish you a very Happy Diwali
Hey Jon
Wish you a very Happy Life

So, if you forget to provide an argument while calling the function, default values for the arguments can be set to cover up.

PHP Function Returning Values

PHP functions can return results. Functions that are defined to perform some mathematical operation, etc., therefore we want to output the result of the operation; hence we return the result.

The return statement can be used for returning any variable or value from a function in PHP.

Example:

<?php

function add($a, $b)
{
    $sum = $a + $b;
    // returning the result
    return $sum;
}

echo "5 + 10 = " . add(5, 10) . "";

?>

Output:

5 + 10 = 15

PHP Function Overloading

It allows you to have multiple different variants of one function, differentiated by the number and type of arguments they take.

For instance, the function add() is defined as taking two arguments and returning the sum of those two. What if you want to provide support for adding three numbers.

To handle such situations, what you can do is you can define two different variants of the function add(), one that accepts two arguments and another that takes three arguments. It is called Function Overloading.

Example:

<?php
// add function with 2 arguments
function add($a, $b)
{
    $sum = $a + $b;
    // returning the result
    return $sum;
}

// overloaded add function with 3 arguments
function add($a, $b, $c) 
{
    $sum = $a + $b + $c;
    // returning the result
    return $sum;
}

// calling add with 2 arguments
echo "5 + 10 = " . add(5, 10) . "<br/>";

// calling add with 3 arguments
echo "5 + 10 + 15 = " .add(5, 10, 15) . "<br/>";

?>

Output:

5 + 10 = 15
5 + 10 + 15 = 30

Note: Function Overloading is not supported by PHP.

It was just to provide you with an idea about function overloading. In PHP, function signatures do not include the argument list and are only based on their names; hence, it is impossible to have two functions with the same name.

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