PHP PDO::setAttribute Method

last modified April 19, 2025

The PDO::setAttribute method in PHP configures database connection behavior. It allows setting various attributes that control how PDO operates.

Basic Definition

PDO::setAttribute sets an attribute on the database connection handle. Attributes control aspects like error handling, case sensitivity, and more.

Syntax: PDO::setAttribute(int $attribute, mixed $value): bool. The method takes an attribute constant and its value, returning true on success.

Setting Error Mode to Exceptions

This example shows how to configure PDO to throw exceptions on errors.

set_error_mode.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    // This will throw an exception if table doesn't exist
    $pdo->query('SELECT * FROM non_existent_table');
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

Setting PDO::ATTR_ERRMODE to PDO::ERRMODE_EXCEPTION makes PDO throw exceptions. This is the recommended error handling mode for development environments.

Enabling Persistent Connections

This demonstrates how to enable persistent database connections.

persistent_connection.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password', [
        PDO::ATTR_PERSISTENT => true
    ]);
    
    // Or set it after connection
    $pdo->setAttribute(PDO::ATTR_PERSISTENT, true);
    
    echo "Using persistent connection";
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}

Persistent connections remain open after script execution, reducing overhead. They can be set in constructor options or via setAttribute. Use with caution.

Setting Default Fetch Mode

This shows how to set the default fetch mode for all queries.

default_fetch_mode.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
    
    $stmt = $pdo->query('SELECT * FROM users LIMIT 1');
    $user = $stmt->fetch(); // Will use FETCH_ASSOC
    
    print_r($user);
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

PDO::ATTR_DEFAULT_FETCH_MODE sets how rows are fetched by default. PDO::FETCH_ASSOC returns results as associative arrays without numeric indices.

Configuring Case Sensitivity

This example demonstrates controlling column name case sensitivity.

case_sensitivity.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_CASE, PDO::CASE_LOWER);
    
    $stmt = $pdo->query('SELECT firstName FROM users LIMIT 1');
    $user = $stmt->fetch(PDO::FETCH_ASSOC);
    
    // Column name will be lowercase
    echo $user['firstname'];
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

PDO::ATTR_CASE forces column names to a specific case. PDO::CASE_LOWER makes all column names lowercase. PDO::CASE_UPPER makes them uppercase.

Setting Connection Timeout

This shows how to configure the connection timeout for PDO.

connection_timeout.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_TIMEOUT, 5);
    
    echo "Connection timeout set to 5 seconds";
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

PDO::ATTR_TIMEOUT sets the timeout in seconds for connection attempts. Not all drivers support this attribute. Check your database documentation.

Enabling Emulated Prepared Statements

This demonstrates enabling emulated prepared statements in PDO.

emulated_prepared.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
    
    $stmt = $pdo->prepare('SELECT * FROM users WHERE id = ?');
    $stmt->execute([1]);
    $user = $stmt->fetch();
    
    print_r($user);
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

PDO::ATTR_EMULATE_PREPARES makes PDO emulate prepared statements in PHP. This can improve performance but may be less secure with some databases.

Setting String Conversion

This example shows how to control string conversion behavior.

string_conversion.php

<?php

declare(strict_types=1);

try {
    $pdo = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
    $pdo->setAttribute(PDO::ATTR_STRINGIFY_FETCHES, true);
    
    $stmt = $pdo->query('SELECT id, name FROM users LIMIT 1');
    $user = $stmt->fetch(PDO::FETCH_ASSOC);
    
    // All values will be strings
    var_dump($user);
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

PDO::ATTR_STRINGIFY_FETCHES converts all fetched data to strings. This is useful when working with numeric data that needs string handling.

Best Practices

Error Handling: Always set ERRMODE_EXCEPTION for safety.
Persistent Connections: Use carefully in high-traffic apps.
Fetch Modes: Set default mode matching your needs.
Case Sensitivity: Be consistent with column name casing.
Timeouts: Set appropriate values for your environment.

Source

PHP PDO::setAttribute Documentation

This tutorial covered the PDO::setAttribute method with practical examples. Understanding these settings helps optimize database interactions in PHP.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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