Digital Communication


Digital Communication

PHP functions: information on their structure and use


When you use a PHP function, you can call the same block of code several times instead of copying the latter each time. This will save you time and be less likely to make errors.

PHP functions: what are they?

PHP functions are designated code blocks which execute a specific instruction, or a series of instructions. They play a fundamental role in structured programming and allow you to divide your PHP code into units that are not only smaller, but also reusable. PHP offers many predefined functions for common tasks, such as working with strings, arrays and PHP loops. You can also customize your own functions if you want to implement specific processes in your applications.

What is the difference between internal and custom PHP functions?

THE internal functions are already integrated into programming languages. For the most part, they are an integral part of their language library, and are therefore immediately available to the developer concerned; no additional steps are then necessary. Conversely, it may be necessary to install specific extensions to use other of these functions. The internal PHP functions are designed in a way to enable efficient execution of general tasks and frequently used operations. The “strlen()” function constitutes a typical example in this regard; this returns the length of a character string. Generally speaking, these functions are optimized to ensure high performance.

Conversely, custom functions correspond to sections of code directly written by the user ; they must therefore be defined explicitly within the code. Most often, these PHP functions are tailored to specific use cases or are used to solve problems specific to a software project. These custom functions may consist of complex algorithms or manipulate certain data. To give a relevant example, some custom functions use PHP to retrieve information from a MySQL database before formatting it for display on a website.

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PHP functions: how are they structured?

Custom PHP functions follow a specific pattern. Below is the basic structure:

function functionName(parameter1, parameter2, ...) {
    // php function example code block
    return result; // optional


Discover with us the different parts of a PHP function:

  • function : this keyword marks the start of the function definition;
  • functionName : this is the name of the function. This must be unique and descriptive as to the objective of the function;
  • parameter1, parameter2, … : the parameters correspond to the values ​​transmitted to the PHP function when it is called. They are optional, and you can use as many as you want;
  • code block : this code allows you to execute the desired task or operations;
  • return result : This is an optional part. If the function must return a result, then this “return” statement should be used.

Internal functions do not need to be defined. To call them, you can directly use their identifier.

Are you new to PHP programming? Do not hesitate to consult our PHP tutorial. If you're not sure whether PHP is the best programming language for you, take a look at our PHP vs. Python and PHP vs. JavaScript comparison articles.


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Application examples of PHP functions

Discover with us some practical uses of PHP functions.

Assign default values ​​to parameters

You can define default values ​​for the parameters of your PHP functions, by entering the desired default value directly when defining the function. If you do not specify a value for this parameter when calling the function, the default value is chosen.

function greet($name = "Tim") {
    echo "Hello, $name";

greet(); // Output: "Hello, Tim"
greet("Max"); // Output: "Hello, Max"


Passing arguments as a reference

The elements are passed to a “by value” or “by reference” function. With the “by value” option, a copy of the affected element is used, and changes do not apply to the original element outside the function. With the “by reference” option, the true value is communicated to the function, and internal modifications to the latter are then carried over to the original value. To use it, you must place the “&” symbol in front of the function definition.

function incrementByOne(&$num) {

$val = 5;


echo $val; // Output: "6"


Here we have chosen to define the function “ incrementByOne » with the parameter $num, transmitted by reference. The post-increment operator is one of the PHP operators; it increments numbers or character strings by 1. When you call the PHP function, the value $val therefore goes from 5 to 6, because the modifications also apply outside the function due to the method of transmission by reference.

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