👨🏼‍💻 Part 7: PHP functions

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What are PHP functions?

In PHP, a function is a block of reusable code designed to perform a specific task. Instead of writing the same code multiple times, you can create a function once and call it whenever needed. This helps keep your code organized, reduces redundancy, and makes your programs easier to maintain.

There are two types of functions in PHP:

  1. Built-in functions – Predefined functions provided by PHP.
  2. User-defined functions – Custom functions created by programmers.

What are PHP functions used for?

Functions in PHP are used for various purposes, such as:

  • Performing calculations.
  • Handling strings and arrays.
  • Processing user input.
  • Connecting to databases.
  • Manipulating files and directories.
  • Generating dynamic web content.

Using functions makes your PHP scripts more structured and efficient.

Common built-in PHP functions

PHP provides a vast number of built-in functions that simplify coding. Here are some essential ones:

1. String functions

  • strlen($string): Returns the length of a string.
  • strtoupper($string): Converts a string to uppercase.
  • strtolower($string): Converts a string to lowercase.

Example:

$text = "Hello World!";
echo strlen($text); // Output: 12
echo strtoupper($text); // Output: HELLO WORLD!

💡 PHP reading exercise – what does this code do?

$mytext = "Hello! This is Sander from Patchstack and I totally did not use ChatGPT for this particular article!";

if ( strlen($mytext) > 30 ) {
   echo "I cannot focus on long texts, sry bro. Can you TLDR?";
}
else {
   echo "What's up?";
}

2. Array functions

  • count($array): Counts the number of elements in an array.
  • array_push($array, $value): Adds a value to an array.
  • array_pop($array): Removes the last element from an array.

Example:

$fruits = ["Apple", "Banana"];
array_push($fruits, "Orange");
print_r($fruits); // Output: Array ( [0] => Apple [1] => Banana [2] => Orange )

3. Mathematical functions

  • round($number): Rounds a number.
  • rand($min, $max): Generates a random number.

Example:

echo rand(1, 100); // Random number between 1 and 100

4. Date and time functions

  • date($format): Formats a date. (like Y-m-d H:i:s)
  • time(): Returns the current timestamp.

Example:

echo date("d.m.Y"); // Output: Current date and time

Creating a custom function in PHP

You can create your own functions in PHP using the function keyword. Here’s an example of a simple custom function:

function greetUser($name) {
    echo "Hello, " . $name . "! Welcome to PHP.";
}

greetUser("Alice"); // Output: Hello, Alice! Welcome to PHP.

Breaking it down:

  1. The function greetUser() is defined with one parameter $name.
  2. The function prints a greeting message.
  3. It is called with the argument "Alice", which outputs a personalized greeting.

Independent exercise

Create a custom PHP function named printMessage() that prints any message you choose when it is called.
Bonus points: In the function, include today’s date. So you will need to echo the date() function inside your custom function.

Result should look like this:

Welcome to learning PHP functions!
Today's date is: 05.12.2025

Try writing this function in a PHP script and run it. Good luck! 🎉

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