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.