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.

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.

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

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

function incrementByOne(&$num) {
    $num++;
}

$val = 5;

incrementByOne($val);

echo $val; // Output: "6"