PHP process model per request - Mini Project: Build & Apply

Understanding PHP Process Model Per Request

📖 Scenario: You are learning how PHP handles web requests. Each time a user visits a PHP page, the server creates a new process to run your PHP code from the start. This means variables and data do not stay between requests unless saved outside the script.

🎯 Goal: Build a simple PHP script that shows how variables reset on each request by counting visits using a session.

📋 What You'll Learn

Create a PHP script with a variable to count visits

Use a session variable to store the visit count

Increment the visit count on each request

Display the current visit count

💡 Why This Matters

🌍 Real World

Websites use PHP sessions to remember users and keep data like login status or shopping carts between page visits.

💼 Career

Understanding PHP's process model and sessions is essential for backend web developers working with PHP to build dynamic, user-friendly websites.

1

Create a PHP script with a visit count variable

Create a PHP file and write code to start a session with session_start(). Then create a variable called visitCount and set it to 0.

PHP

<?php
session_start();
// Your code here

Hint

Use session_start() at the top to enable sessions. Then create $visitCount and set it to 0.

2

Add session variable to store visit count

Add code to check if $_SESSION['visitCount'] exists. If it does, set $visitCount to $_SESSION['visitCount']. Otherwise, keep $visitCount as 0.

PHP

<?php
session_start();
$visitCount = 0;
// Your code here

Hint

Use isset() to check if the session variable exists before using it.

3

Increment the visit count and save it in session

Increase $visitCount by 1. Then save the new value back to $_SESSION['visitCount'].

PHP

<?php
session_start();
$visitCount = 0;
if (isset($_SESSION['visitCount'])) {
    $visitCount = $_SESSION['visitCount'];
}
// Your code here

Hint

Use $visitCount++ to add one, then store it in the session.

4

Display the current visit count

Write a print statement to show the text: "You have visited this page X times." where X is the value of $visitCount.

PHP

<?php
session_start();
$visitCount = 0;
if (isset($_SESSION['visitCount'])) {
    $visitCount = $_SESSION['visitCount'];
}
$visitCount++;
$_SESSION['visitCount'] = $visitCount;
// Your code here

Hint

Use print() with double quotes and include $visitCount inside the string.

Practice

1. What happens to PHP variables after a web request finishes?

easy

A. They become global variables accessible by all users

B. They keep their values for the next request automatically

C. They are stored permanently in the server memory

D. They are reset and lost unless saved externally

Solution

1. Step 1: Understand PHP request lifecycle

   PHP starts fresh for each request, so variables exist only during that request.

2. Step 2: Identify variable persistence

   Variables reset after request ends unless saved in sessions or databases.

3. Final Answer:

   They are reset and lost unless saved externally -> Option D

4. Quick Check:

   PHP variables reset each request = D [OK]

Hint: Remember: PHP starts fresh every request, no variable memory [OK]

Common Mistakes:

• Thinking variables persist automatically between requests
• Confusing PHP with long-running server processes
• Assuming global variables keep values across users

2. Which PHP code snippet correctly shows the start of a new request process?

easy

A.

B.

C.

D.

Solution

1. Step 1: Analyze variable initialization

   In a new request, variables start fresh; $count = 0 sets it properly.

2. Step 2: Check other options for persistence

   Options A, B, D try to increment without initialization or rely on static/session which need extra setup.

3. Final Answer:

   <?php $count = 0; echo $count; ?> -> Option C

4. Quick Check:

   New request means fresh variables = C [OK]

Hint: Fresh request means variables start from scratch [OK]

Common Mistakes:

• Assuming static variables keep value across requests
• Using session without starting it
• Incrementing uninitialized variables

3. What will be the output of this PHP code when run twice in separate requests?

<?php
session_start();
if (!isset($_SESSION['visits'])) {
  $_SESSION['visits'] = 1;
} else {
  $_SESSION['visits']++;
}
echo $_SESSION['visits'];
?>

medium

A. 1 then 2

B. 1 then 1

C. 2 then 3

D. Error on second request

Solution

1. Step 1: Understand session persistence

   Session data keeps values across requests, so visits count increases.

2. Step 2: Trace two requests

   First request sets visits=1; second request increments to 2.

3. Final Answer:

   1 then 2 -> Option A

4. Quick Check:

   Session stores visits count = 1 then 2 [OK]

Hint: Sessions keep data between requests, variables do not [OK]

Common Mistakes:

• Thinking variables persist without sessions
• Forgetting to call session_start()
• Expecting static variables to persist across requests

4. Identify the error in this PHP code snippet that tries to keep a counter across requests:

<?php
$count = 0;
$count++;
echo $count;
?>

medium

A. Variables reset each request, so counter never increases

B. Syntax error due to missing semicolon

C. Session not started, so counter is undefined

D. Static variable needed to keep count

Solution

1. Step 1: Check variable behavior per request

   $count is set to 0 every time, so increment always starts fresh.

2. Step 2: Identify persistence issue

   Without sessions or external storage, counter resets each request.

3. Final Answer:

   Variables reset each request, so counter never increases -> Option A

4. Quick Check:

   Variables reset each request = A [OK]

Hint: Variables reset each request; use sessions to persist [OK]

Common Mistakes:

• Assuming static variables persist across requests
• Confusing syntax errors with logic errors
• Forgetting to start sessions for persistence

5. You want to count unique visitors to your PHP website. Which approach correctly uses PHP's process model per request to achieve this?

hard

A. Use a static variable in PHP script to count visitors

B. Store visitor count in a database and increment on each request

C. Increment a PHP variable without sessions or storage

D. Rely on PHP variables to keep count across requests

Solution

1. Step 1: Understand PHP process model limits

   PHP variables reset each request, so they can't keep visitor count.

2. Step 2: Identify persistent storage method

   Database stores data permanently and can be updated each request.

3. Final Answer:

   Store visitor count in a database and increment on each request -> Option B

4. Quick Check:

   Persistent storage needed for visitor count = A [OK]

Hint: Use database or sessions to save data beyond request [OK]

Common Mistakes:

• Using static or normal variables expecting persistence
• Ignoring need for external storage
• Confusing sessions with static variables