Returns all remaining rows as an array according to the requested fetch mode.
The objective is to understand the behavior and operational limits, not only the method name.
What It Does
Returns all remaining rows as an array according to the requested fetch mode.
Syntax and Return Value
PDOStatement::fetchAll(Parameter #0 [ <optional> int $mode = PDO::FETCH_DEFAULT ], Parameter #1 [ <optional> mixed ...$args ]): mixedThe return value and exceptional cases depend on the call described here: Large result sets can exhaust memory; fetch one row at a time when streaming.
Example 1: Basic Use
The statement has a real query and result set; database-specific metadata and statement options may be unsupported.
<?php
$pdo = new PDO('sqlite::memory:', null, null, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
$pdo->exec('CREATE TABLE products (id INTEGER PRIMARY KEY, name TEXT NOT NULL, price INTEGER NOT NULL, active INTEGER)');
$pdo->exec("INSERT INTO products (id,name,price,active) VALUES (1,'Desk',120,1),(2,'Lamp',35,1),(3,'Chair',85,0)");
$stmt = $pdo->prepare("SELECT id, name, price FROM products WHERE id >= :min ORDER BY id");
$stmt->execute(["min" => 1]);
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
echo json_encode($rows);Example 2: A Second Scenario
The statement has a real query and result set; database-specific metadata and statement options may be unsupported.
<?php
$pdo = new PDO('sqlite::memory:', null, null, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
$pdo->exec('CREATE TABLE products (id INTEGER PRIMARY KEY, name TEXT NOT NULL, price INTEGER NOT NULL, active INTEGER)');
$pdo->exec("INSERT INTO products (id,name,price,active) VALUES (1,'Desk',120,1),(2,'Lamp',35,1),(3,'Chair',85,0)");
$stmt = $pdo->prepare("SELECT id, name, price FROM products WHERE id >= :min ORDER BY id");
$stmt->execute(["min" => 2]);
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
echo json_encode($rows);Example 3: Practical Checks
The statement has a real query and result set; database-specific metadata and statement options may be unsupported.
<?php
$pdo = new PDO('sqlite::memory:', null, null, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
$pdo->exec('CREATE TABLE products (id INTEGER PRIMARY KEY, name TEXT NOT NULL, price INTEGER NOT NULL, active INTEGER)');
$pdo->exec("INSERT INTO products (id,name,price,active) VALUES (1,'Desk',120,1),(2,'Lamp',35,1),(3,'Chair',85,0)");
$stmt = $pdo->prepare("SELECT id, name, price FROM products WHERE id >= :min ORDER BY id");
$stmt->execute(["min" => 3]);
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);
echo json_encode($rows);Important Behavior and Edge Cases
Large result sets can exhaust memory; fetch one row at a time when streaming.
For production use, also account for error handling, data validation, resource limits and environment-specific driver behavior.
Comparison with Related Approaches
| Approach | Important distinction |
|---|---|
| PDOStatement::fetchAll | Returns all remaining rows as an array according to the requested fetch mode. |
| Related API / pattern | fetch retrieves one row per call. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Assuming the happy path covers edge cases | Large result sets can exhaust memory; fetch one row at a time when streaming. |
| Using a related API interchangeably | fetch retrieves one row per call. |
Key Takeaways
- Returns all remaining rows as an array according to the requested fetch mode.
- Large result sets can exhaust memory; fetch one row at a time when streaming.
- fetch retrieves one row per call.
Choose this API or pattern when its exact semantics match your task, and verify the result against the database driver and runtime used by your application.