How to Fix WordPress "Error Establishing a Database Connection": Complete Guide
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Publisher ID: ca-pub-XXXXXXXXXXXXXXXX (Configured in config.php)This classic WordPress error occurs when WordPress PHP files cannot authenticate or exchange data with the MySQL/MariaDB database server. The issue typically involves incorrect credentials in wp-config.php or corrupted database tables.
Open your "wp-config.php" file and verify the four core constants: DB_NAME, DB_USER, DB_PASSWORD, and DB_HOST. Test these credentials using a small standalone test script. If credentials are correct, check whether visiting "/wp-admin" displays "One or more database tables are unavailable", and add "define('WP_ALLOW_REPAIR', true);" to repair them.
📋 Guide Table of Contents
1. Problem Diagnosis & Symptoms
Every dynamic page load in WordPress queries the MySQL database for posts and theme options. When mysqli_connect fails inside the wpdb class, WordPress immediately aborts rendering.
2. Primary Root Causes
- Cause: Incorrect database password in wp-config.php.
- Cause: Corrupted database tables.
3. Step-by-Step Diagnostic Fixes
Inspect wp-config.php Database Constants
Check DB_NAME, DB_USER, DB_PASSWORD, and DB_HOST.
define( 'DB_NAME', 'wp_db' );
define( 'DB_USER', 'wp_user' );
define( 'DB_PASSWORD', 'Password123' );
define( 'DB_HOST', 'localhost' );4. How to Verify the Resolution
- Load WordPress homepage and WP-Admin.
5. Diagnostic Troubleshooting Matrix
| Symptom Observed | Root Cause | Recommended Action |
|---|---|---|
| wp-admin says: One or more tables are unavailable | Database tables corrupted | Add WP_ALLOW_REPAIR to wp-config.php and run repair.php |
6. Critical Mistakes to Avoid
- ❌ Never leave WP_ALLOW_REPAIR permanently enabled.
7. Frequently Asked Questions
❓ What should DB_HOST be in Hostinger?
On Hostinger, DB_HOST is "localhost".
Official Technical References
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