PHP

PHP Fundamentals: An Introduction to PHP

Jeremy Duncan

Jeremy Duncan

— 3 min read
PHP Fundamentals: An Introduction to PHP


PHP (PHP: Hypertext Preprocessor) is a server-side scripting language designed for web development but also used as a general-purpose programming language. It enables developers to create dynamic content that interacts with databases. PHP is notable for its ease of use, extensive feature set, and strong community support.

PHP Fundamentals and Examples

Syntax

Basic syntax involves PHP tags, comments, and standard HTML integration.

<?php
// This is a single-line comment
echo "Hello, World!"; // Outputs: Hello, World!
?>

Variables

Variables in PHP are declared with a $ sign followed by the variable name.

<?php
$name = "John";
$age = 25;
?>

Data Types

PHP supports several data types including strings, integers, floats, booleans, arrays, and objects.

<?php
$string = "Hello";
$integer = 10;
$float = 10.5;
$boolean = true;
?>

Strings

Operations on strings, such as concatenation and various string functions.

<?php
$greeting = "Hello";
$name = "Alice";
echo $greeting . " " . $name; // Outputs: Hello Alice
?>

Arrays

PHP allows indexed, associative, and multi-dimensional arrays.

<?php
$colors = array("red", "green", "blue");
echo $colors[0]; // Outputs: red

$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
echo $age['Ben']; // Outputs: 37
?>

Control Structures

Includes if-else statements, switch cases, and loops (for, while, do-while, foreach).

<?php
for ($x = 0; $x <= 10; $x++) {
    echo "The number is: $x <br>";
}
?>

Functions

Defining and calling functions.

<?php
function familyName($fname) {
    echo "$fname Refsnes.<br>";
}
familyName("Jani");
?>

Superglobals

PHP superglobals are built-in variables that are always accessible.

<?php
echo $_SERVER['HTTP_USER_AGENT'];
?>

Form Handling

Handling data from forms using POST and GET methods.

<?php
// "welcome.php"
echo "Welcome " . $_POST['name'];
?>

File Inclusion

Including and requiring files in scripts.

<?php
include 'header.php';
require 'functions.php';
?>

File Handling

Reading and writing files.

<?php
$file = fopen("testfile.txt", "w");
$txt = "Hello World";
fwrite($file, $txt);
fclose($file);
?>

Sessions and Cookies

Managing sessions and cookies for maintaining state.

<?php
session_start();
$_SESSION['favcolor'] = 'green';
?>

Error Handling

Custom error handling and exceptions.

<?php
function customError($errno, $errstr) {
    echo "<b>Error:</b> [$errno] $errstr";
}
set_error_handler("customError");
?>

Database Access

Connecting to databases like MySQL.

<?php
$conn = new mysqli($servername, $username, $password, $dbname);
?>

Regular Expressions

Utilizing regular expressions for pattern matching.

<?php
$str = "Visit W3Schools";
$pattern = "/w3schools/i";
echo preg_match($pattern, $str); // Outputs: 1
?>

Object-Oriented Programming

PHP supports OOP concepts such as classes, objects, inheritance, etc.

<?php
class Car {
    function Car() {
        $this->model = "VW";
    }
}
$herbie = new Car();
echo $herbie->model;
?>

Conclusion

Mastering these fundamentals will significantly improve your ability to develop robust PHP applications and enhance your overall understanding of server-side programming.

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