PHP PDOStatement::setFetchMode() Method: Usage and Examples

Configures the default way future fetch calls shape rows.

The objective is to understand the behavior and operational limits, not only the method name.

What It Does

Configures the default way future fetch calls shape rows.

Syntax and Return Value

PDOStatement::setFetchMode(Parameter #0 [ <required> int $mode ], Parameter #1 [ <optional> mixed ...$args ]): mixed

The return value and exceptional cases depend on the call described here: It does not fetch any rows by itself; use fetch or fetchAll afterward.

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]);
$stmt->setFetchMode(PDO::FETCH_ASSOC);
echo json_encode($stmt->fetch());

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]);
$stmt->setFetchMode(PDO::FETCH_ASSOC);
echo json_encode($stmt->fetch());

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]);
$stmt->setFetchMode(PDO::FETCH_ASSOC);
echo json_encode($stmt->fetch());

Important Behavior and Edge Cases

It does not fetch any rows by itself; use fetch or fetchAll afterward.

For production use, also account for error handling, data validation, resource limits and environment-specific driver behavior.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Configures the default way future fetch calls shape rows.
• It does not fetch any rows by itself; use fetch or fetchAll afterward.
• fetch(PDO::FETCH_ASSOC) chooses a mode for a single 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.