🔹 1. How WordPress Uses PHP

WordPress is built entirely on PHP + MySQL. Every page you visit — whether it’s a blog post or contact page — is dynamically generated using PHP templates and queries to the database.

✅ PHP in WordPress handles:

• Loading content from the database
• Applying your theme’s design
• Running plugin functions
• Displaying posts, users, menus, and widgets

In short, PHP = the engine of WordPress.

🔹 2. Understanding the WordPress Theme Structure

Typical theme folder:

/wp-content/themes/my-theme/
│
├── style.css
├── functions.php
├── header.php
├── footer.php
├── index.php
├── single.php
├── page.php
└── archive.php

Each .php file plays a role in the template hierarchy — the logic WordPress uses to decide which template to load.

🧩 Template Hierarchy Example

🧠 WordPress looks for the most specific file first. If it doesn’t find it, it “falls back” to the next most general one.

🔹 3. The WordPress Loop

The Loop is how WordPress dynamically displays posts using PHP.

<?php if ( have_posts() ) : ?>
  <?php while ( have_posts() ) : the_post(); ?>
    <h2><?php the_title(); ?></h2>
    <div><?php the_content(); ?></div>
  <?php endwhile; ?>
<?php else : ?>
  <p>No posts found.</p>
<?php endif; ?>

✅ Each post passes through this loop — pulling title, content, date, author, etc., from the database.

🔹 4. functions.php – The Heart of Theme Functionality

functions.php is like your theme’s mini plugin. It allows you to add new PHP functionality without editing WordPress core files.

Common uses:

• Enqueue scripts and styles
• Add custom image sizes
• Register menus and widgets
• Create shortcodes and custom functions

🧩 Example: Enqueue Styles

<?php
function streetgeek_enqueue_styles() {
    wp_enqueue_style( 'main-style', get_stylesheet_uri() );
}
add_action( 'wp_enqueue_scripts', 'streetgeek_enqueue_styles' );

✅ Adds your CSS stylesheet properly the WordPress way.

🧩 Example: Register Menu

function streetgeek_register_menu() {
    register_nav_menu( 'main-menu', __( 'Main Menu' ) );
}
add_action( 'init', 'streetgeek_register_menu' );

🔹 5. Creating a Custom Shortcode

A shortcode is a small PHP function that users can insert into posts or pages like this:

[streetgeek_hello]

Let’s create one inside functions.php:

function streetgeek_hello_shortcode() {
    return "<h3>Hello from StreetGeek Academy!</h3>";
}
add_shortcode( 'streetgeek_hello', 'streetgeek_hello_shortcode' );

✅ Now you can add [streetgeek_hello] to any WordPress post or page and it will output your message.

Shortcode with Attributes

function streetgeek_greet_shortcode( $atts ) {
    $atts = shortcode_atts(
        array( 'name' => 'Student' ),
        $atts
    );
    return "<p>Welcome, " . esc_html( $atts['name'] ) . "! Keep learning PHP!</p>";
}
add_shortcode( 'streetgeek_greet', 'streetgeek_greet_shortcode' );

✅ Example usage:

[streetgeek_greet name="Yogi"]

Outputs:

Welcome, Yogi! Keep learning PHP!

🔹 6. Building Your First Plugin

You can move your shortcode into a standalone plugin.

Step 1: Create Plugin Folder

/wp-content/plugins/streetgeek-hello/

Step 2: Add File streetgeek-hello.php

<?php
/*
Plugin Name: StreetGeek Hello
Plugin URI: https://streetgeek.academy
Description: A simple WordPress plugin that greets users.
Version: 1.0
Author: Yogi
*/

function streetgeek_hello_shortcode() {
    return "<h3>Hello, StreetGeek Developer!</h3>";
}
add_shortcode( 'streetgeek_hello', 'streetgeek_hello_shortcode' );

✅ Go to Dashboard → Plugins → StreetGeek Hello → Activate
Now [streetgeek_hello] works across the entire site.

🔹 7. Security and Best Practices

• Always use esc_html() or esc_attr() when outputting data.
• Use nonces for form verification.
• Never use direct database queries — use the WordPress database API ($wpdb) instead.
• Don’t edit core WordPress files — use themes, child themes, or plugins.

🔹 8. WordPress Database with PHP

Every WordPress site runs on MySQL. You can interact with it safely using the $wpdb global object.

global $wpdb;
$results = $wpdb->get_results(
    "SELECT * FROM $wpdb->posts WHERE post_status = 'publish'"
);
foreach ( $results as $post ) {
    echo "<p>" . esc_html( $post->post_title ) . "</p>";
}

✅ Retrieves and displays all published posts from your site.

🧩 HANDS-ON PRACTICE

Exercise 1: Create a Shortcode

Add this in your functions.php:

function streetgeek_thanks_shortcode() {
    return "<p>Thank you for completing the PHP Foundations Course!</p>";
}
add_shortcode( 'streetgeek_thanks', 'streetgeek_thanks_shortcode' );

✅ Add [streetgeek_thanks] to a post — it should render your message.

Exercise 2: Create a Plugin

Follow the earlier plugin steps and make your own version:

• Plugin Name: StreetGeek Welcome
• Shortcode: [streetgeek_welcome name="YourName"]

✅ Output a personalized message like:
Welcome back, Yogi — ready for the next level!

Exercise 3: Use The Loop in a Custom Template

Create home.php in your theme:

<?php get_header(); ?>
<h1>Latest StreetGeek Posts</h1>
<?php
if ( have_posts() ) :
  while ( have_posts() ) : the_post();
    echo "<h2><a href='" . get_permalink() . "'>" . get_the_title() . "</a></h2>";
    echo "<p>" . get_the_excerpt() . "</p>";
  endwhile;
else :
  echo "<p>No posts found.</p>";
endif;
?>
<?php get_footer(); ?>

✅ Displays all recent posts with links and excerpts.

🧾 Module 13 Quiz

💪 CHALLENGE TASK – StreetGeek Hello Plugin 2.0

Objective: Build an upgraded WordPress plugin using PHP functions and shortcode logic.

Requirements:

• Create plugin folder streetgeek-hello-2
• Create streetgeek-hello-2.php
• Add the following code:

<?php
/*
Plugin Name: StreetGeek Hello 2.0
Description: Displays a personalized welcome message.
Version: 2.0
Author: StreetGeek Academy
*/

function streetgeek_hello2_shortcode( $atts ) {
    $atts = shortcode_atts(
        [ 'name' => 'StreetGeek Student' ],
        $atts
    );
    $message = "Welcome back, " . esc_html( $atts['name'] ) . "! Keep building.";
    return "<div style='padding:10px; background:#0E477B; color:#fff;'>$message</div>";
}
add_shortcode( 'streetgeek_hello2', 'streetgeek_hello2_shortcode' );

Upload, activate, and use [streetgeek_hello2 name="Yogi"].

✅ Output:
Welcome back, Yogi! Keep building.

🧾 SUBMISSION CHECKLIST

• ✅ Shortcode [streetgeek_thanks] working in theme
• ✅ Custom plugin created and activated
• ✅ Loop-based template displaying posts
• ✅ Quiz completed
• ✅ Challenge plugin functioning

🏁 GRADUATION 🎓

Congratulations! You’ve completed the StreetGeek Academy PHP Foundations Course and built the skills
to create plugins, themes, and dynamic apps.

🚀 You now know:

• PHP syntax, logic, arrays, and functions
• File, form, and database integration
• Sessions, authentication, and error handling
• How PHP powers WordPress under the hood

Next steps at StreetGeek Academy:

• Enroll in WordPress Development Foundations
• Advance to JavaScript for WordPress Developers
• Join the StreetGeek Certified Developer Track