What is PHP - Visual Explanation

Concept Flow - What is PHP

User requests a web page

↓

Web server receives request

↓

Server runs PHP code

↓

PHP processes data and logic

↓

PHP sends HTML output

↓

Browser displays the page

PHP runs on the web server to process code and send back HTML for the browser to show.

Execution Sample

PHP

<?php
  echo "Hello, world!";
?>

This PHP code sends the text 'Hello, world!' to the browser.

Execution Table

Step	Action	Code Executed	Output Produced
1	Start PHP script	<?php
2	Execute echo statement	echo "Hello, world!";	Hello, world!
3	End PHP script	?>

💡 PHP script ends and output is sent to browser

Variable Tracker

Variable	Start	After echo	Final
No variables	-	-	-

Key Moments - 2 Insights

Why does PHP code run on the server and not in the browser?

PHP is a server-side language, so it runs on the web server before the page is sent to the browser, as shown in the concept flow and execution table steps 1 and 3.

What does the echo statement do in PHP?

Echo sends text to the output that the browser will display, as seen in execution table step 2 where 'Hello, world!' is produced.

Visual Quiz - 3 Questions

Look at the execution table, what output is produced at step 2?

A PHP code

B No output

C Hello, world!

D Error message

💡 Hint

Check the 'Output Produced' column at step 2 in the execution table.

At which step does the PHP script end?

A Step 2

B Step 3

C Step 1

D There is no end

💡 Hint

Look at the 'Action' column for the step where PHP script ends.

If we add a variable to store 'Hello', where would it appear in the variable tracker?

A In all columns after it is set

B In the 'Start' column

C In the 'Final' column

D In the 'After echo' column

💡 Hint

Variables change over time, so track their values from start to final in the variable tracker.

Concept Snapshot

PHP is a server-side language.
It runs on the web server.
PHP code generates HTML output.
Use <?php ... ?> tags.
Echo sends output to browser.
Browser shows the final page.

Full Transcript

PHP is a programming language that runs on a web server. When a user asks for a web page, the server runs PHP code to create the page content. The PHP code can do things like show text or work with data. After running, PHP sends the result as HTML to the user's browser. The browser then shows the page. For example, the PHP code '<?php echo "Hello, world!"; ?>' sends the text 'Hello, world!' to the browser. PHP code runs step by step on the server, starting with the PHP tags, then the echo command, and finally ending the script. Variables in PHP can hold data and change as the code runs. This process helps make web pages dynamic and interactive.

Practice

1. What is PHP mainly used for?

easy

A. Designing static images

B. Editing videos

C. Writing desktop applications

D. Creating dynamic and interactive websites

Solution

1. Step 1: Understand PHP's purpose

   PHP is a language designed to create dynamic content on websites, making them interactive.

2. Step 2: Compare options

   Only Creating dynamic and interactive websites matches PHP's main use; others relate to different fields.

3. Final Answer:

   Creating dynamic and interactive websites -> Option D

4. Quick Check:

   PHP = Dynamic websites [OK]

Hint: PHP is for web interaction, not static or media tasks [OK]

Common Mistakes:

• Thinking PHP edits images or videos
• Confusing PHP with desktop app languages

2. Which of these is the correct way to start PHP code in a file?

easy

A. <?php

B. <script>

C. <php>

D. <?html>

Solution

1. Step 1: Recall PHP opening tags

   PHP code starts with <?php to tell the server to run PHP.

2. Step 2: Check other tags

   <script> is for JavaScript, <php> and <?html> are invalid.

3. Final Answer:

   <?php -> Option A

4. Quick Check:

   PHP code starts with <?php [OK]

Hint: PHP always starts with <?php tag [OK]

Common Mistakes:

• Using <script> instead of PHP tags
• Writing <php> which is not valid

3. What will this PHP code output?

<?php
 echo "Hello, World!";
?>

medium

A. Syntax Error

B. Hello, World!

C. <?php echo "Hello, World!"; ?>

D. Nothing

Solution

1. Step 1: Understand echo statement

   The echo command prints the text inside quotes to the browser.

2. Step 2: Check code correctness

   The code is correct PHP syntax and will output the string exactly.

3. Final Answer:

   Hello, World! -> Option B

4. Quick Check:

   echo prints text = Hello, World! [OK]

Hint: echo prints text inside quotes [OK]

Common Mistakes:

• Expecting PHP code to show as text
• Thinking code causes error without semicolon

4. Find the error in this PHP code:

<?php
 echo "Welcome to PHP!"
?>

medium

A. Echo cannot print strings

B. Wrong opening PHP tag

C. Missing semicolon after echo statement

D. Quotes should be single quotes

Solution

1. Step 1: Check PHP syntax rules

   Each statement must end with a semicolon to separate commands.

2. Step 2: Identify missing semicolon

   The echo line lacks a semicolon at the end, causing a syntax error.

3. Final Answer:

   Missing semicolon after echo statement -> Option C

4. Quick Check:

   Statements end with ; = Missing semicolon [OK]

Hint: Every PHP statement ends with a semicolon [OK]

Common Mistakes:

• Ignoring semicolon at line end
• Thinking double quotes cause error

5. You want to create a PHP page that shows the current year dynamically. Which code snippet correctly does this?

hard

A. <?php echo date('Y'); ?>

B. <?php print currentYear(); ?>

C. <?php echo 'year'; ?>

D. <?php showYear(); ?>

Solution

1. Step 1: Identify PHP function for current year

   The built-in function date('Y') returns the current year as a string.

2. Step 2: Check code snippets

   Only <?php echo date('Y'); ?> uses date('Y') correctly with echo to print the year.

3. Final Answer:

   <?php echo date('Y'); ?> -> Option A

4. Quick Check:

   date('Y') prints year = <?php echo date('Y'); ?> [OK]

Hint: Use date('Y') to get current year in PHP [OK]

Common Mistakes:

• Using undefined functions like currentYear()
• Printing literal strings instead of function output