Fetching results (fetch, fetchAll) in PHP - Step-by-Step Execution

Concept Flow - Fetching results (fetch, fetchAll)

Execute Query

↓

Fetch One Row?

No→Exit

Yes↓

Return Row Data

↓

Fetch Next Row or fetchAll

↩Back to Fetch One Row or Return All Rows

This flow shows how PHP fetches data from a database query, either one row at a time or all rows at once.

Execution Sample

PHP

<?php
$stmt = $pdo->query('SELECT id, name FROM users');
$row = $stmt->fetch();
$allRows = $stmt->fetchAll();
?>

This code runs a query, fetches one row, then fetches all remaining rows.

Execution Table

Step	Action	Method Called	Result	Notes
1	Run query 'SELECT id, name FROM users'	query()	PDOStatement object	Query executed, ready to fetch
2	Fetch first row	fetch()	Array with first row data	Returns one row as associative array
3	Fetch all remaining rows	fetchAll()	Array of arrays with remaining rows	Returns all rows left in result set
4	Try fetch again	fetch()	false	No more rows, fetch returns false
5	Try fetchAll again	fetchAll()	Empty array	No rows left, returns empty array

💡 No more rows to fetch, fetch returns false and fetchAll returns empty array

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5
$stmt	null	PDOStatement object	PDOStatement object	PDOStatement object	PDOStatement object
$row	null	First row array	First row array	false	false
$allRows	null	null	Array of remaining rows	Array of remaining rows	Empty array

Key Moments - 3 Insights

Why does fetch() return false after fetching all rows?

Because fetch() moves forward one row at a time and returns false when no rows remain, as shown in step 4 of the execution_table.

What does fetchAll() return if called after all rows are fetched?

It returns an empty array since there are no rows left to fetch, as shown in step 5 of the execution_table.

Does fetchAll() include the row already fetched by fetch()?

No, fetchAll() returns only the rows remaining after fetch() has moved the pointer, so the first row is not included, as seen between steps 2 and 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of $row after step 2?

A An empty array

B false

C An array with the first row data

D PDOStatement object

💡 Hint

Check the 'Result' column in step 2 of execution_table.

At which step does fetch() return false?

A Step 3

B Step 4

C Step 5

D Step 2

💡 Hint

Look at the 'Result' column for fetch() in execution_table steps.

If fetch() was not called before fetchAll(), what would fetchAll() return at step 3?

A All rows from the query

B Only the first row

C An empty array

D false

💡 Hint

Recall that fetchAll() returns all rows left; if none fetched yet, it returns all rows.

Concept Snapshot

PHP fetch() gets one row from query result as an array.
fetchAll() gets all remaining rows as an array of arrays.
fetch() returns false when no rows left.
fetchAll() returns empty array if no rows left.
Use fetch() to process rows one by one.
Use fetchAll() to get all rows at once.

Full Transcript

This visual trace shows how PHP fetches data from a database query using fetch() and fetchAll(). First, the query runs and returns a PDOStatement object. Then fetch() gets the first row as an array. Next, fetchAll() gets all remaining rows as an array of arrays. If fetch() is called again after all rows are fetched, it returns false. If fetchAll() is called again, it returns an empty array. This helps understand how to retrieve data step-by-step or all at once from a database in PHP.