Basic Syntax of PHP Functions

A PHP function is structured as follows:

function my_function_name(input1, input2) {

…function body…

}

Here’s a breakdown of the components:

• function: This keyword indicates that a function is being defined.
• my_function_name: This is the identifier you will use to call the function. Ensure that the name starts with a letter (a-z) or an underscore and is descriptive enough to convey its purpose without needing comments.
• (input1, input2): These parentheses contain the parameters required for the function. If no parameters are necessary, simply use empty parentheses.
• {…}: Curly brackets enclose the code that the function will execute.

Returning Values from Functions

All actions within a function are performed in a local scope. To send a value back to the global scope of the script, you must use the return keyword. If you omit it, the function will return NULL by default.

//Example 1

function greet() {

return "Hello";

}

echo greet(); //Outputs "Hello"

//Example 2

function farewell() {

return "Goodbye";

}

echo farewell(); //Outputs NULL

It's important to note that once the return statement is executed, no further code in that function will run. Therefore, ensure that return is positioned as the last command in your function.

Input Parameters for Enhanced Functionality

Input parameters maximize the utility of functions. These parameters are declared within the parentheses of the function definition. You can declare multiple parameters by separating them with commas, and optional parameters can be enclosed in square brackets.

Here's an example to clarify:

function welcome($customer_name="Guest") {

echo "Hello $customer_name!";

}

welcome("Stef"); //Outputs "Hello Stef!"

welcome(); //Outputs "Hello Guest!"

Variable Scope Within Functions

Variables defined within a function maintain their values in the global scope. For instance:

$my_num = 8;

function double_num($num) {

$my_num = $num * 2;

return $my_num;

}

$new_num = double_num($my_num);

echo $my_num; //Outputs 8

echo "n";

echo $new_num; //Outputs 16

Only variables declared within the function are accessible by default. Attempting to use a global variable will result in an error unless you declare it as global:

$car_wheels = 4;

function total_wheels($num_of_cars) {

global $car_wheels;

return $car_wheels * $num_of_cars;

}

echo total_wheels(6); //Outputs 24

Challenges with Global Variables

In complex code, relying on global variables can create confusion. For example:

$num_of_staff = 100;

//Function 1: Calculates based on inputs

function hoursTotal($num_of_staff, $hours_worked) {

return $num_of_staff * $hours_worked;

}

echo hoursTotal(5, 20); //Outputs 100

//Function 2: Utilizes a global variable

function daysTotal($days_worked) {

global $num_of_staff;

return $num_of_staff * $days_worked;

}

echo daysTotal(20); //Outputs 2000

In larger projects, it may be difficult to track the origin of a global variable, leading to potential errors. While global variables can be useful, caution and clear documentation are recommended for readability.

Leveraging Built-in PHP Functions

PHP is equipped with thousands of built-in functions that streamline programming tasks. You can invoke these functions similarly to your custom ones by calling their names along with any required parameters. For instance, the date() function retrieves the current date and time based on the specified format.

echo date("jS F Y"); //For example, this might return - 19th April 2022

This concludes our discussion on functions. I hope you found it informative. If you're keen on mastering PHP, follow along with the rest of the articles in this series.

PHP Functions Tutorial - Learn PHP Programming - This video tutorial provides a deep dive into PHP functions, essential for any aspiring programmer.

Future Reading

For further learning, consider checking out my other PHP articles (updated as they are published):

• Should You Still Learn PHP in 2022?
• PHP 101: Fundamentals
• PHP 101: Functions
• PHP 101: Arrays
• PHP 101: Conditionals
• PHP 101: Loops (coming soon)
• PHP 101: Form Handling (coming soon)
• PHP 101: Classes and Objects (coming soon)
• PHP 101: My First Project (coming soon)

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