Script execution and memory reset in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What happens to variables in PHP after a script finishes executing?

All variables and data stored in memory during the script execution are cleared. PHP resets memory for the next script run.

beginner

Why does PHP reset memory after each script execution?

To ensure each script runs fresh without leftover data, preventing unexpected behavior and improving security.

beginner

Can data persist between PHP script executions without external storage?

No. PHP does not keep data in memory between runs. To persist data, you must use files, databases, or sessions.

intermediate

How does PHP handle memory during script execution?

PHP allocates memory for variables and data as the script runs, then frees all memory when the script ends.

intermediate

What is the role of the PHP garbage collector in script execution?

The garbage collector frees memory used by variables no longer referenced during script execution, helping manage memory efficiently.

What happens to PHP variables after the script finishes?

A They are saved automatically to a file

B They stay in memory for the next script

C They are cleared from memory

D They become global variables

PHP clears all variables from memory after the script ends to start fresh next time.

Which of these is needed to keep data between PHP script runs?

A Using sessions or databases

B Relying on PHP memory reset

C Declaring variables as static

D Nothing, PHP keeps data automatically

Sessions, files, or databases are needed to store data beyond one script execution.

When does PHP free memory used by variables?

A At the end of script execution

B Only when the server restarts

C When the user closes the browser

D Never, memory is permanent

PHP frees all memory used by variables when the script finishes running.

What is the PHP garbage collector's job?

A Save variables to disk automatically

B Prevent script execution

C Restart the script if memory is low

D Free memory from unused variables during script run

The garbage collector frees memory from variables no longer needed while the script runs.

Why is memory reset important in PHP script execution?

A To keep data for the next user

B To avoid leftover data causing bugs

C To slow down the server

D To save data automatically

Resetting memory prevents old data from affecting new script runs, avoiding bugs and security issues.

Explain what happens to memory and variables when a PHP script finishes running.

Think about how PHP treats data after the script ends.

Describe how you can keep data between PHP script executions despite memory reset.

Memory reset means data disappears, so what tools help keep data?

Practice

1. What happens to variables in a PHP script after the script finishes running?

easy

A. Variables are saved permanently in the script file

B. Variables keep their values until the server restarts

C. All variables and memory are reset and cleared

D. Variables are shared with other scripts automatically

Solution

1. Step 1: Understand PHP script execution

   PHP runs scripts from top to bottom each time the page loads.

2. Step 2: Memory and variable reset after execution

   After the script finishes, all variables and memory used are cleared to keep the environment clean.

3. Final Answer:

   All variables and memory are reset and cleared -> Option C

4. Quick Check:

   PHP resets variables after script ends = C [OK]

Hint: Remember PHP resets memory after each script run [OK]

Common Mistakes:

• Thinking variables keep values between page loads
• Assuming variables save to the script file
• Believing variables are shared across scripts automatically

2. Which of the following is the correct way to start a PHP script that resets variables each time it runs?

easy

A.

B.

C.

D. // PHP code here

Solution

1. Step 1: Identify correct PHP tags

   PHP scripts start with to run properly.

2. Step 2: Understand script resets

   Each time the script runs, variables reset automatically without extra commands.

3. Final Answer:

   -> Option A

4. Quick Check:

   Correct PHP tags = A [OK]

Hint: Use tags to start PHP scripts [OK]

Common Mistakes:

• Using <script> tags which are for JavaScript
• Trying to call reset() function which doesn't reset variables
• Using incorrect <php> tags

3. Consider this PHP code run twice in a row (two separate page loads):

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

What will be the output each time the script runs?

medium

A. 1 then 1

B. 0 then 1

C. 1 then 2

D. 0 then 0

Solution

1. Step 1: Analyze variable initialization

   Each time the script runs, $counter is set to 0 at the start.

2. Step 2: Increment and output

   $counter++ increases $counter to 1, then echo prints 1 each time.

3. Final Answer:

   1 then 1 -> Option A

4. Quick Check:

   Variables reset each run, so output is 1 each time [OK]

Hint: Variables reset each run, so counter restarts at 0 [OK]

Common Mistakes:

• Assuming $counter keeps incrementing across runs
• Confusing pre-increment and post-increment
• Thinking echo prints 0 first

4. You wrote this PHP code:

<?php
$sum = 10;
$sum += 5;
?>

But after refreshing the page, $sum is always 15. You want $sum to keep increasing by 5 each time the page loads. What is the problem?

medium

A. You need to use a loop to increase $sum

B. The += operator does not add values correctly

C. You forgot to declare $sum as global

D. PHP resets variables after each script run, so $sum starts at 10 every time

Solution

1. Step 1: Understand variable reset behavior

   PHP clears all variables after each script finishes, so $sum resets to 10 every time.

2. Step 2: Why $sum does not keep increasing

   Because $sum is reinitialized to 10 on each page load, adding 5 results in 15 always.

3. Final Answer:

   PHP resets variables after each script run, so $sum starts at 10 every time -> Option D

4. Quick Check:

   Variables reset each run = D [OK]

Hint: Variables reset each run; use sessions or files to keep values [OK]

Common Mistakes:

• Thinking += operator is faulty
• Assuming global declaration keeps value between runs
• Believing loops affect variable persistence

5. You want to count how many times a PHP page has been loaded by visitors. Since PHP resets variables each run, which method should you use to keep the count across page loads?

hard

A. Declare the count variable as global inside the script

B. Store the count in a session or a file/database to persist data

C. Use a loop to increment the count variable inside the script

D. Reset the count variable to zero at the start of the script

Solution

1. Step 1: Recognize PHP variable reset limitation

   PHP variables reset after each script run, so count cannot persist in normal variables.

2. Step 2: Use persistent storage

   Sessions, files, or databases store data between page loads to keep count.

3. Final Answer:

   Store the count in a session or a file/database to persist data -> Option B

4. Quick Check:

   Persistent storage needed for count across runs = B [OK]

Hint: Use sessions or files to save data between page loads [OK]

Common Mistakes:

• Thinking global variables keep values between runs
• Trying to use loops for persistence
• Resetting variables each time defeats counting