How a PHP request starts and ends - Practice Exercises

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP script?

Consider this PHP code that runs during a request. What will it output?

PHP

<?php
register_shutdown_function(function() {
    echo "End of request.";
});
echo "Start of request.";
?>

A End of request.Start of request.

B Start of request.End of request.

C Start of request.

D End of request.

💡 Hint

Think about when the shutdown function runs in relation to the main script.

The main script prints "Start of request." first. The shutdown function runs after the script finishes, printing "End of request." so the combined output is "Start of request.End of request.".

🧠 Conceptual

intermediate

What happens first when a PHP request starts?

When a PHP request begins, which of these happens first?

A PHP parses and compiles the script into opcodes

B The session is destroyed

C The shutdown functions are called

D The script outputs HTML to the browser

💡 Hint

Think about what PHP must do before running your code.

PHP first reads the script and compiles it into opcodes before executing any code or sending output.

❓ Predict Output

advanced

What error does this PHP code produce?

This PHP script tries to use a variable after the request ends. What error will it produce?

PHP

<?php
register_shutdown_function(function() use (&$var) {
    echo $var;
});
$var = "Hello";
?>

A Fatal error: Cannot use variable in shutdown function

B Undefined variable: var

C Hello

D No output

💡 Hint

Variables used with 'use' in shutdown functions keep their value.

The shutdown function captures $var by reference before the script ends, so it can output "Hello" without error.

🧠 Conceptual

advanced

Which PHP event marks the end of a request?

Which of these best describes when a PHP request ends?

A When the PHP interpreter starts parsing the script

B When the server receives the HTTP request

C When the user closes the browser tab

D When the script finishes execution and all output is sent

💡 Hint

Think about what happens after your PHP code runs.

A PHP request ends after the script finishes running and all output is sent to the client.

🔧 Debug

expert

Why does this PHP script output only 'Start' and not 'End'?

This PHP script tries to print 'End' at the end of the request but it doesn't appear. Why?

PHP

<?php
register_shutdown_function(function() {
    echo "End";
});
exit("Start");
?>

A Because exit() outputs 'Start' and then shutdown functions run normally

B Because echo inside shutdown functions is ignored

C Because exit() stops the script immediately and shutdown functions are not called

D Because shutdown functions run before exit()

💡 Hint

Think about how exit() works with shutdown functions.

exit() outputs 'Start' and then triggers shutdown functions, so 'End' is printed after 'Start'. The output is 'StartEnd'. If 'End' is missing, it may be due to output buffering or environment.

Practice

1. What marks the beginning of PHP code in a file?

easy

A. The <php> tag

B. The <script> tag

C. The <?php tag

D. The <?> tag

Solution

1. Step 1: Identify PHP opening tag

   PHP code always starts with the <?php tag to tell the server to process PHP.

2. Step 2: Compare with other tags

   Other tags like <script> are for JavaScript, and <php> is invalid.

3. Final Answer:

   The <?php tag -> Option C

4. Quick Check:

   PHP starts with <?php [OK]

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

Common Mistakes:

• Confusing PHP tags with HTML or JavaScript tags
• Using short tags like which may be disabled
• Thinking PHP starts with ? or other symbols

2. Which of the following correctly ends a PHP block?

easy

A. ?>

B. </php>

C. <?php

D. <?>

Solution

1. Step 1: Identify PHP closing tag

   The PHP block ends with ?> to signal the end of PHP code.

2. Step 2: Validate other options

   </php> is invalid HTML, <?php starts PHP, and <?> is not a valid closing tag.

3. Final Answer:

   ?> -> Option A

4. Quick Check:

   PHP ends with ?> [OK]

Hint: PHP ends with ?> tag to close code block [OK]

Common Mistakes:

• Using HTML closing tags like
• Confusing PHP start and end tags
• Omitting the closing tag when mixing PHP and HTML

3. What will be the output of this PHP code?

<?php
echo 'Hello';
?>

medium

A. Hello

B. <?php echo 'Hello'; ?>

C. Syntax Error

D. No output

Solution

1. Step 1: Understand PHP code execution

   The PHP code inside <?php ?> runs on the server and outputs the string 'Hello'.

2. Step 2: Check output behavior

   The echo statement prints 'Hello' to the page, so the output is exactly that.

3. Final Answer:

   Hello -> Option A

4. Quick Check:

   echo 'Hello' outputs Hello [OK]

Hint: echo prints text inside PHP tags to the page [OK]

Common Mistakes:

• Expecting PHP code to show as text in browser
• Confusing PHP tags with HTML tags
• Thinking PHP code causes syntax error without semicolon

4. Identify the error in this PHP snippet:

<?php
echo 'Hi'
?>

medium

A. Incorrect PHP start tag

B. Using single quotes instead of double quotes

C. Missing closing PHP tag

D. Missing semicolon after echo statement

Solution

1. Step 1: Check PHP syntax rules

   Each PHP statement must end with a semicolon; here, echo 'Hi' lacks it.

2. Step 2: Validate other parts

   The start tag <?php and closing tag ?> are correct; single quotes are valid in PHP.

3. Final Answer:

   Missing semicolon after echo statement -> Option D

4. Quick Check:

   Statements need semicolon [OK]

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

Common Mistakes:

• Forgetting semicolon at end of statements
• Thinking PHP tags are case-sensitive
• Assuming quotes type causes syntax error

5. Which statement best describes how a PHP request lifecycle works?

hard

A. PHP code runs once when the server starts and stays in memory

B. Each request runs PHP code fresh, then ends after sending response

C. PHP code runs only if the closing tag is omitted

D. PHP code runs continuously until manually stopped

Solution

1. Step 1: Understand PHP request lifecycle

   PHP runs code fresh on each page request, processes it, then ends after sending the response.

2. Step 2: Evaluate other options

   PHP does not run continuously or stay in memory; closing tag presence does not control execution.

3. Final Answer:

   Each request runs PHP code fresh, then ends after sending response -> Option B

4. Quick Check:

   PHP runs per request, then ends [OK]

Hint: PHP runs fresh on each request, then stops [OK]

Common Mistakes:

• Thinking PHP code runs persistently like a service
• Believing PHP runs only if closing tag is missing
• Assuming PHP code stays loaded between requests