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📜 | Introduction to PHP

What is PHP?​

PHP, which stands for "PHP: Hypertext Preprocessor," is a scripting language primarily designed for web development. PHP was created in 1995 with its first version developed by Rasmus Lerdorf, and since then, it has evolved significantly to become one of the most widely used scripting languages for web development. Written in C, PHP leverages the performance and flexibility offered by this low-level language while providing a simpler syntax that is more accessible to web developers. The current version, 8.3.9, includes numerous improvements and new features compared to its predecessors, such as performance optimizations, security enhancements, and modern programming capabilities. With these regular updates, PHP continues to adapt to the evolving needs of modern web development and remains a relevant choice for server-side development.

Scripting

Unlike traditional programming languages that require the creation of complete programs, a scripting language like PHP is used to write small scripts or files that perform specific actions on a web server.

Interpreted

PHP is interpreted, meaning that the code is executed line by line by an interpreter, unlike compiled languages (such as C, C++, or Java) where the source code is transformed into machine/binary code before execution.

Cross-platform

PHP is cross-platform, which means that it can run on different operating systems, similar to Java.

Object-Oriented Programming

It also supports Object-Oriented Programming (OOP), allowing the creation of classes, objects, and the use of concepts like inheritance and polymorphism.

Weakly Typed

PHP is weakly typed (or loosely typed), which means that variable data types are not strictly defined and can be changed dynamically (e.g., an int can become a string), making code writing easier but sometimes leading to subtle errors.

Server-Side Execution

Note that PHP only runs on the server side: the code is interpreted on the server, and then the result is sent back to the client (web browser), making it an ideal language for creating dynamic web pages.

Client-Server Diagram

Coding in PHP​

tip

Always keep the PHP documentation close by

  • Extension ".php"
  • All variables start with $, e.g., $my_var
  • Semicolon at the end of lines
  • Naming convention is snake_case, e.g., my_super_function
  • All files start with <?php, and can end with ?>
  • It is possible to include <?php ... ?> tags in HTML (always in a .php file)
<div>
    <p>My paragraph</p>
    <div><?php echo $my_var; ?></div>
</div>

Example of PHP code:

<?php

$my_var = 12;

if ($my_var == 12) {
    echo "Hello!\n";
}
else {
    $my_var = null;
}

PHP Differences​

Echo​

Printing with echo (don't forget to add a \n for a new line, as it does not automatically go to the next line)

$my_var = "toto";
echo $my_var;
echo "Hi there, $my_var\n";

echo.png

Debug​

Debug a variable with var_dump(). This function displays the complete content of the variable when called, helping to identify and fix any issues.

$my_var = [1, 2, 5];
var_dump($my_var);

var_dump.png

For each​

The for each loop ("for each")

$my_values = [1, 2, 3, 4];

foreach ($my_values as $var) {
    echo "$var\n";
}
🖥️ Output
1
2
3
4

It is also possible to use a key

$my_values = [10, 11, 12, 13];

foreach ($my_values as $index => $var) {
    echo "$index: $var\n";
}
🖥️ Output
0: 10
1: 11
2: 12
3: 13

Match​

Newer, the match statement

$my_var = 2;

$my_other_var = match ($my_var) {
    1, 2 => "toto",
    $my_var > 10 => "tata",
    default => "default case"
};

echo $my_other_var;
🖥️ Output
toto

Associative Arrays​

To create arrays with custom indexes (like a dictionary)

$my_var = [
    0 => "toto",
    "my index 1" => "tata",
    "my other index" => "uncle" 
];

echo $my_var["my other index"];
🖥️ Output
uncle

"." Operator for String Concatenation​

To add/concatenate strings in PHP, we use the . operator

echo "my string 1" . "my string 2";
🖥️ Output
my string 1my string 2
X

Graph View