Why variables do not persist between requests in PHP - Visual Breakdown

Concept Flow - Why variables do not persist between requests

Start Request 1

↓

Set variable $x = 5

↓

End Request 1 - Script stops

↓

Start Request 2

↓

Variable $x does NOT exist

↓

Set $x again or error

↓

End Request 2

Each web request runs a new PHP script instance, so variables set in one request are lost when it ends.

Execution Sample

PHP

<?php
$x = 5;
echo $x;
?>

This code sets $x to 5 and prints it during one request.

Execution Table

Step	Action	Variable $x	Output
1	Start Request 1	undefined
2	Set $x = 5	5
3	Print $x	5	5
4	End Request 1	5 (lost after script ends)
5	Start Request 2	undefined
6	Try to print $x	undefined	Error or empty
7	Set $x = 10	10
8	Print $x	10	10
9	End Request 2	10 (lost after script ends)

💡 Each request ends and clears all variables; no persistence between requests.

Variable Tracker

Variable	Start Request 1	After Step 2	After Step 4	Start Request 2	After Step 7	After Step 9
$x	undefined	5	lost	undefined	10	lost

Key Moments - 2 Insights

Why does $x lose its value after the first request ends?

Because PHP runs each request as a new script instance, all variables are cleared when the script finishes (see execution_table step 4).

Can variables keep their values automatically between requests?

No, variables do not persist automatically; you must use sessions, cookies, or databases to save data between requests.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of $x at the start of Request 2?

A undefined

B 5

C 10

D Error

💡 Hint

Check execution_table row 5 'Start Request 2' shows $x as undefined.

At which step does the variable $x get lost after being set?

A Step 6

B Step 3

C Step 4

D Step 7

💡 Hint

Look at execution_table step 4 where the request ends and variables are lost.

If you want $x to keep its value between requests, what should you do?

A Declare $x as global

B Use sessions or cookies

C Set $x again in each request

D Nothing, it persists automatically

💡 Hint

Refer to key_moments about persistence methods beyond normal variables.

Concept Snapshot

PHP variables exist only during one request.
When the script ends, all variables are cleared.
Each new request starts fresh with no previous variables.
To keep data between requests, use sessions, cookies, or databases.
Variables do NOT persist automatically across requests.

Full Transcript

In PHP, each web request runs the script from start to end. Variables like $x exist only during that request. When the request finishes, the script stops and all variables are lost. The next request starts fresh with no memory of previous variables. This is why $x set in one request is undefined in the next. To keep data between requests, you must use special storage like sessions or cookies. This example shows $x set to 5 in the first request and lost after it ends. In the second request, $x is undefined until set again. This behavior is normal and important to understand for web programming.