Aim

To write a program that passes control to another page using include and require, and terminates execution with exit() and die().

Theory

Real sites are assembled from parts — header, navigation, config, footer — pulled into each page with PHP's file-inclusion constructs. Both evaluate another PHP file as if its code were pasted at that point, so functions and constants it defines become available; the difference is failure behaviour:

• include emits a warning when the file is missing and the script continues — right for optional fragments (a promo banner, a footer).
• require raises a fatal error and stops the script — right for files the page cannot work without (configuration, database credentials).
• include_once/require_once remember what has already been loaded and skip repeats, preventing "function already declared" fatals when shared files include each other.

Termination: exit() ends the script immediately; an optional string argument is printed first (an integer argument becomes the process exit code instead). die() is a pure alias of exit() — identical behaviour, conventionally used on failure paths. The classic idiom $conn or die("message") exploits short-circuit evaluation: if the left operand is truthy, or never evaluates the right side; if it is falsy, die() runs and the script stops. The @ operator seen before include suppresses the warning a missing file would print.

Requirements

• XAMPP/WAMP with PHP 8.x, or PHP CLI
• Code editor (VS Code); browser or terminal

Procedure

1. Start Apache from the XAMPP Control Panel.
2. Save the snippet as p09_include_require.php in C:\xampp\htdocs\wbplab.
3. Run http://localhost/wbplab/p09_include_require.php or php p09_include_require.php.
4. Remove the @ before include "missing_page.php" to see the warning, then change that include to require and watch the script die with a fatal error instead of continuing.
5. Flip $isLoggedIn to false to trigger the exit() branch, and $dbConnected to true to let the final line run.

Explanation of the Code

• The script first writes its own helper pages into sys_get_temp_dir() with file_put_contents(), so the demo is self-contained: header.php defines showHeader(), and config.php defines the constants STUDENT and EMAIL.
• include $headerFile; pulls in the function definition; calling showHeader() afterwards proves the included code is now part of this script.
• @include "missing_page.php"; fails silently (@ mutes the warning) and the next echo demonstrates that execution continued — the defining property of include.
• require $configFile; loads the mandatory constants, then prints them; had the file been missing, nothing after this line would run.
• exit() is guarded by if (!$isLoggedIn) — since $isLoggedIn is true, the script skips termination and prints that fact.
• Finally, $dbConnected or die("...") fires because $dbConnected is false: the message prints and the script stops, so the last echo never executes.

Expected Output

The run prints: Welcome, Rohit! | rohit@example.com, then Script continues after failed include., then Student: Rohit Kumar | Email: rohit@example.com, then Rohit is logged in. exit() was skipped., then Connecting to database for Rohit... followed by DB connection failed for rohit@example.com. Script terminated. — and nothing more: the line This line will never execute. is unreachable because die() ended the script.

🎯 Viva Questions

1. include vs require on a missing file? include warns and continues; require throws a fatal error and stops.
2. When would you choose require_once? For shared files (config, function libraries) that might be pulled in from several places — it prevents duplicate-definition fatals.
3. Is there any difference between die() and exit()? No — die is a language alias of exit; the choice is purely stylistic.
4. How does $dbConnected or die("msg") work? or short-circuits: the right operand runs only when the left is falsy, so die() fires exactly on failure.
5. What does the @ operator do? Suppresses the error message the following expression would emit — convenient in demos, discouraged in production because it hides problems.
6. What happens to code defined in an included file? It joins the including script's scope — its functions, classes and constants become directly callable.

CO Mapping

CO1, CO2