PHP: Hypertext Preprocessor, a Core Language Driving Full-Stack Development

PHP is one of many languages, not spoken but typed. Its longevity and widespread adoption have made it a staple in the toolkit of many full-stack developers, particularly those working on web-based projects.

Many programming tutorials on web-related languages typically commence with HTML. However, this time, we’re diving straight into PHP. Here, we won’t delve into the historical background of programming languages; that’s a topic for another day. Today, as part of our Full-Stack Series, we’re immersing ourselves fully in PHP.

Before we proceed, if you’re new here, I encourage you to explore our previous posts in this series. In our last two instalments, we delved into “The Full-Stack: Exploring the Role of Programming in Application Development” and “The Full-Stack Symphony: Orchestrating a Powerful Application“. Our blog index covers not only programming topics but also a wide array of other subjects, from product articles to Bible study.

PHP stands for “Hypertext Preprocessor.” It’s a recursive acronym, where the first letter stands for the abbreviation itself. As you might recall from our previous discussions, PHP is a backend language. It operates on the server side, generating output for the front end. While PHP seamlessly interacts with databases, such as MySQL, to collect and store data, it’s important to note that PHP cannot execute front-end functionalities.

In PHP code, it’s common to encounter a blend of other languages. This is because PHP often dynamically generates content. Later in this post, we’ll explore various methods of embedding other languages within PHP code.

The Global PHP Overview

PHP enjoys widespread usage, with numerous variations of the language available. Some notable examples include:

• Facebook’s Evolution: Initially, PHP served as Facebook’s primary programming language for web development. However, the company later introduced Hack, a statically typed variant of PHP. Designed to bolster the efficiency and security of PHP code in large-scale applications, Hack incorporates features such as static typing, generics, and performance optimizations.
• WordPress Dominance: WordPress, a leading content management system (CMS), relies heavily on PHP as its server-side scripting language. While PHP forms the backbone of WordPress, the platform also integrates other technologies like MySQL for database management and JavaScript for client-side interactions. Additionally, WordPress offers its own set of functions, classes, and APIs, empowering developers to interact seamlessly with the platform.
• Joomla!’s Adaptation: Similar to WordPress, Joomla! is a popular CMS predominantly written in PHP. However, Joomla! distinguishes itself by introducing the Joomla! Framework, a bespoke collection of PHP libraries and packages. This framework equips developers with tools beyond content management, facilitating the creation of diverse web applications.

These examples merely scratch the surface of PHP’s versatility. In this post, we aim to provide overviews and summaries, refraining from exhaustive details. Future posts may delve deeper into specific aspects of PHP. For now, let’s explore an index of the PHP language:

PHP Language Index

• Basic Syntax:
  • PHP Tags (<?php and ?>)
  • Comments (single line // and multi-line /* */)
• Variables:
  • Declared with $ followed by name (letters, numbers, underscores, starting with a letter)
• Data Types:
  • String (text)
  • Integer (whole numbers)
  • Float (decimal numbers)
  • Boolean (true or false)
  • Array (ordered collection of items)
• Operators:
  • Arithmetic (+, -, *, /)
  • Comparison (==, !=, <, >)
  • Logical (&&, ||, !)
  • Assignment (=, +=, -=)
• Control Flow Statements:
  • if statements
  • else statements
  • else if statements
  • for loops
  • while loops
  • foreach loops
• Functions:
  • Reusable blocks of code
  • Can take parameters and return values
• Error Handling:
  • Identifying and handling errors during execution
• Forms Handling:
  • Processing user input submitted through forms (GET and POST methods)
• File Handling:
  • Reading from and writing to files on the server
• String Manipulation:
  • Functions for working with text data (e.g., strlen, strpos, substr)
• Date and Time Handling:
  • Functions for working with dates and times (e.g., date, time, strtotime)
• Object-Oriented Programming (OOP):
  • Concepts like classes, objects, inheritance, polymorphism
• Database Access:
  • Interacting with databases using extensions like PDO or MySQLi
• Regular Expressions:
  • Patterns for matching and manipulating text
• Security:
  • Techniques to prevent vulnerabilities in your code (e.g., user input validation)
• Sessions and Cookies:
  • Managing user state across requests

The Foundation of PHP

In PHP, understanding its basic syntax lays the foundation for effective coding. Let’s delve into the essentials:

1. Basic Syntax:

PHP Tags: PHP code is typically embedded within HTML documents using PHP tags. These tags signal the server to interpret the enclosed code as PHP instructions. The two primary PHP tags are <?php to open PHP code and ?> to close it.

<?php
    // PHP code goes here
?>

Comments: Comments are essential for code documentation and readability. PHP supports both single-line (//) and multi-line (/* */) comments.

Single-line comments are preceded by // and are ideal for brief annotations or explanations within the code:

// This is a single-line comment

Multi-line comments are enclosed between /* and */ and are suitable for longer explanations or comments spanning multiple lines:

/*
    This is a multi-line comment
    It can span across multiple lines
*/

    It can span across multiple lines

2. Variables:

In PHP, variables serve as placeholders for storing data. They allow for dynamic and flexible manipulation of data within a script. Variables are declared using the dollar sign ($) followed by the variable name. Variable names can consist of letters, numbers, and underscores, but must start with a letter. Think of variables as a single storage bin that can keep data.

<?php

    $name = "John"; // String variable

    $age = 25; // Integer variable

    $price = 10.99; // Float variable

    $is_admin = true; // Boolean variable

?>

Variables enable PHP scripts to adapt to changing data, providing dynamic outputs based on various conditions or user inputs. They play a crucial role in making PHP scripts versatile and capable of handling diverse tasks.

Data and the Bricks and Mortar of PHP

In the realm of programming, data serves as the fundamental building blocks upon which software applications are constructed. Understanding data types, operators, and control flow statements is akin to grasping the essential elements of a programming language like PHP. In this section, we explore these foundational concepts, demystifying their purpose, usage, and significance.

What is Data?

Data refers to raw facts, information, or statistics collected, stored, and processed by computers. In the context of programming and computer science, data is the foundation upon which software applications are built and operated. It can take various forms, such as text, numbers, images, or multimedia files, and is manipulated and analysed to derive meaningful insights or perform specific tasks.

In essence, data encompasses everything from simple values like names and numbers to more complex structures like databases and datasets. It serves as the input for algorithms and functions, allowing software systems to perform calculations, make decisions, and produce outputs.

Understanding and effectively managing data is crucial in the field of programming, as it forms the basis for developing software solutions, creating user interfaces, and facilitating communication between different components of a system. Whether it’s storing user information in a database, processing sensor readings from a device, or displaying multimedia content on a website, data lies at the heart of virtually every aspect of computing.

Data Types

Data types in PHP define the nature of the information that can be stored and manipulated within a script. PHP supports various data types, each tailored to accommodate different kinds of data. Let’s delve into the most common data types:

1. String:

Strings represent textual data enclosed within single quotes (‘ ‘) or double quotes (” “). They are used to store and manipulate sequences of characters, such as words, sentences, or even entire paragraphs.

$name = "John";
$message = 'Hello, world!';

2. Integer: 

Integers are used to represent whole numbers without any decimal or fractional components. They are commonly employed for counting, indexing, or performing arithmetic operations that involve whole quantities.

$age = 25;

$quantity = 10;

3. Float: 

Floats, also known as floating-point numbers, are used to represent numbers with decimal or fractional components. They are essential for handling values that require precision beyond whole numbers, such as monetary amounts or scientific measurements.

$price = 10.99;
$temperature = -3.5;

4. Boolean: 

Booleans are a binary data type that can have one of two possible values: true or false. They are indispensable for logical operations, conditional statements, and decision-making within PHP scripts.

$is_active = true;
$is_admin = false;

5. Array:

Arrays are versatile data structures used to store collections of related items. They provide a convenient means of organising and accessing multiple values under a single variable name. Arrays can contain elements of various data types, allowing for flexible data management.

Example:

$fruits = array("Apple", "Banana", "Orange");

$student = array("name" => "John", "age" => 25, "grade" => "A");

Manipulating Data

Operators

Operators in PHP are symbols or keywords used to perform operations on operands, such as variables or values. They enable programmers to manipulate data, make comparisons, and control the flow of execution within a script. Let’s explore the different categories of operators:

1. Arithmetic Operators:

Arithmetic operators are used to perform mathematical operations, such as addition (+), subtraction (-), multiplication (*), and division (/). They are fundamental for numeric calculations and computations within PHP scripts.

Example:

$a = 10;

$b = 5;

$sum = $a + $b; // 15

$difference = $a - $b; // 5

$product = $a * $b; // 50

$quotient = $a / $b; // 2

2. Comparison Operators:

Comparison operators are employed to compare two values and determine their relationship. Common comparison operators include equality (==), inequality (!=), less than (<), and greater than (>). They are vital for implementing conditional logic and decision-making in PHP scripts.

Example:

$x = 10;

$y = 5;

$is_equal = ($x == $y); // false

$is_greater = ($x > $y); // true

$is_not_equal = ($x != $y); // true

3. Logical Operators: 

Logical operators are used to combine multiple conditions and evaluate the truthfulness of expressions. Examples of logical operators include AND (&&), OR (||), and NOT (!). They are indispensable for creating complex logical conditions and controlling program flow based on multiple criteria.

Example:

$is_valid = ($age >= 18 && $age <= 60); // true if age is between 18 and 60

$is_admin_or_moderator = ($is_admin || $is_moderator); // true if user is admin or moderator

4. Assignment Operators:

Assignment operators are used to assign values to variables. They include the basic assignment operator (=) as well as compound assignment operators such as addition assignment (+=), subtraction assignment (-=), and so on. Assignment operators streamline the process of assigning and updating variable values within PHP scripts.

Example:

$total = 100;

$discount = 20;

$total -= $discount; // $total is now 80

Executing and Controlling Instructions

Control Flow Statements

Control flow statements in PHP dictate the order in which instructions are executed within a script. They enable programmers to implement conditional logic, loops, and branching mechanisms, thereby controlling the flow of program execution. Let’s explore some of the essential control flow statements:

1. if Statements:

if statements are used to execute a block of code if a specified condition is true. They are fundamental for implementing decision-making and branching logic within PHP scripts.

Example:

if ($age >= 18) {

    echo "You are eligible to vote.";

}

2. else Statements:

else statements are paired with if statements to execute a block of code if the preceding condition evaluates to false. They provide an alternative execution path when the primary condition is not met.

Example:

if ($age >= 18) {

    echo "You are eligible to vote.";

} else {

    echo "You are not eligible to vote.";

}

3. else if Statements:

else if statements are used to evaluate additional conditions if the preceding if statement’s condition is false. They allow for the sequential evaluation of multiple conditions within a single control flow structure.

Example:

if ($grade >= 90) {

    echo "Excellent!";

} else if ($grade >= 80) {

    echo "Good!";

} else {

    echo "Needs Improvement!";

}

4. for Loops:

for loops are used to execute a block of code a specified number of times. They are ideal for iterating over a range of values or processing elements within an array.

Example:

for ($i = 0; $i < 5; $i++) {

    echo "Iteration: $i <br>";

}

5. while Loops:

while loops are used to execute a block of code as long as a specified condition is true. They are useful for repetitive tasks where the number of iterations is not predetermined.

Example:

$i = 0;

while ($i < 5) {

    echo "Iteration: $i <br>";

    $i++;

}

6. foreach Loops:

foreach loops are specifically designed for iterating over the elements of an array. They simplify the process of traversing array elements and performing operations on each element individually.

Example:

$fruits = array("Apple", "Banana", "Orange");

foreach ($fruits as $fruit) {

    echo "$fruit <br>";

}

In essence, mastering data types, operators, and control flow statements equips aspiring programmers with the essential tools needed to construct robust and dynamic PHP applications. These foundational concepts serve as the bedrock upon which more advanced programming techniques and methodologies are built.

In Conclusion

To wrap up, this article has covered the essential PHP concepts, providing a solid foundation for building PHP applications. By mastering these basics, you’re now well-equipped to start creating your own projects and exploring more advanced topics. We sincerely appreciate your engagement and dedication in following along with this content.

In our upcoming post, we’ll dive into some exciting topics, including functions, error handling, and forms handling. Stay tuned for more in-depth discussions and practical examples that will further shed light on the exciting world of PHP.

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Remember: “Success is not final, failure is not fatal: It is the courage to continue that counts.” – Winston Churchill

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