How to debug PDO database queries?

php

debugging

pdo

database-queries

byNikita Barsukov·Jan 19, 2025

Boost PDO debugging by setting error mode to throw exceptions: employ PDO::ATTR_ERRMODE and PDO::ERRMODE_EXCEPTION:

$pdo = new PDO($dsn, $user, $pass, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
// Now maybe your code will complain loud enough for you to hear the problem!

Upon query failure, exceptions come to your rescue. Catch them to eliminate the problem swiftly:

try {
    // Your PDO query execution here
} catch (PDOException $e) {
    // How poetic, your code is finally expressive. Next time, let's avoid the drama, shall we?
    die('Query failed: ' . $e->getMessage());
}

For non-exception errors, use the errorInfo() method on your statement object:

if ($stmt->execute() === false) {
    list(, ,$errorMsg) = $stmt->errorInfo();
    echo 'Query error: ' . $errorMsg; // Ah! The sweet smell of clear, descriptive error messages!
}

Debugging decoded

Three magic steps in debugging PDO

Reading Errors: Get acquainted with your errors. No, don't avoid them!
Inspecting Binding: Eye through your bound variables. Trust me, it's thrilling!
Understanding Query: Yes, talking to your database. A cool party trick, right?

Unveiling errors with `debugDumpParams`

Observe a suspicious binding statement? Get verification with debugDumpParams().

$stmt->debugDumpParams();
// Looks like your statement decided to spill the beans.

This method proudly presents the query and parameters, granting an insightful inspection.

Reconstructing your query

The elusive "real" SQL query is, alas, not served on a silver platter due to PDO's prepared statements. Fear not! You have the manual reconstruction:

echo $query; // SQL query with placeholders, acting innocent.
var_dump($params); // Array of bound variables showing their true colors!

Security and performance measures

Remember to switch off error logging and disable debug mode in a production environment. You wouldn't want to host unwanted performance parties and leave your house (logs) open for unsolicited invasions, would you?

Mastering debugging techniques

Harnessing the native powers of your database

Mystery lover? Good databases inundate you with enigmatic queries. Configure your database to log the thrilling queries. Consider it your personal detective novel.

Crafting your debugging function

Cause who doesn't love foiling a tricky bug? A custom made function like pdo_sql_debug will aid in formatting and logging queries, turning you into a smooth debugging superstar.

Capitalizing on advanced debugging tools

Want to feel like 007 in the debugging world? Leverage the power of Xdebug! It's like having a magnifying glass, revealing details you didn't know existed.

explain-codes / Php / How to debug PDO database queries?

Linked

Sqlstate[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax — PHP — PDO



How can I prevent SQL injection in PHP?



How can I with mysqli make a query with LIKE and get all results?



How do I obtain raw SQL from a query builder?



Log the actual SQL query using ActiveRecord with Yii2?

