Transaction management in PHP - Step-by-Step Execution

Concept Flow - Transaction management

Start Transaction

↓

Execute Queries

↓

Check for Errors?

Yes→Rollback Transaction

↓

End Transaction

↓

Commit Transaction

↓

End

This flow shows starting a transaction, running queries, checking for errors, and either committing or rolling back.

Execution Sample

PHP

<?php
$conn->beginTransaction();
$conn->exec("INSERT INTO users(name) VALUES('Alice')");
if ($conn->errorCode() != '00000') {
  $conn->rollBack();
} else {
  $conn->commit();
}
?>

This PHP code starts a transaction, inserts a user, and commits or rolls back based on error.

Execution Table

Step	Action	Transaction State	Query Executed	Error Detected	Result
1	Begin transaction	Active	None	No	Transaction started
2	Execute INSERT query	Active	INSERT INTO users(name) VALUES('Alice')	No	Query successful
3	Check for errors	Active	None	No	No errors found
4	Commit transaction	Committed	None	No	Transaction committed
5	End	Committed	None	No	Transaction complete

💡 Transaction ends after commit because no errors were detected.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
Transaction State	None	Active	Active	Active	Committed	Committed
Error Detected	False	False	False	False	False	False

Key Moments - 3 Insights

Why do we need to start a transaction before executing queries?

Starting a transaction groups queries so they can be committed or rolled back together, as shown in Step 1 of the execution_table.

What happens if an error is detected after executing queries?

If an error occurs, the transaction is rolled back to undo all changes, but in this example no error occurs (Step 3).

Why do we commit the transaction only after checking for errors?

Committing finalizes changes only if all queries succeed, ensuring data integrity, as shown in Step 4.

Visual Quiz - 3 Questions

Look at the execution_table, what is the transaction state after Step 2?

A Active

B Committed

C Rolled back

D None

💡 Hint

Check the 'Transaction State' column in the execution_table at Step 2.

At which step does the transaction get committed?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look for the 'Commit transaction' action in the execution_table.

If an error was detected at Step 3, what would happen next?

A Commit transaction

B Rollback transaction

C Execute another query

D End without commit or rollback

💡 Hint

Refer to the concept_flow where error detection leads to rollback.

Concept Snapshot

Transaction management in PHP:
- Use beginTransaction() to start.
- Execute queries inside transaction.
- Check for errors.
- Use commit() if no errors.
- Use rollBack() if errors occur.
Ensures all-or-nothing data changes.

Full Transcript

This example shows how PHP manages database transactions. First, beginTransaction() starts a transaction. Then, queries run inside it. After queries, the code checks for errors. If no errors, commit() saves changes permanently. If errors occur, rollBack() undoes all changes. This process ensures data stays correct and consistent.