Fix: mysqli_connect(): Access denied error in PHP - Quick Solutions

The ‘mysqli_connect(): Access denied’ error occurs when PHP cannot connect to MySQL due to incorrect credentials, host, or user permissions. This error prevents database connections.

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Common Causes and Fixes

1. Wrong Username/Password

<?php
// ❌ Error: Wrong credentials
$connection = mysqli_connect("localhost", "wronguser", "wrongpass", "database");
?>

<?php
// ✅ Fixed: Correct credentials
$connection = mysqli_connect("localhost", "correctuser", "correctpass", "database");
?>

2. Wrong Host

<?php
// ❌ Error: Wrong host
$connection = mysqli_connect("wronghost", "user", "pass", "database");  // Error!
?>

<?php
// ✅ Fixed: Correct host
$connection = mysqli_connect("localhost", "user", "pass", "database");
// OR
$connection = mysqli_connect("127.0.0.1", "user", "pass", "database");
?>

3. Wrong Database Name

<?php
// ❌ Error: Database doesn't exist
$connection = mysqli_connect("localhost", "user", "pass", "nonexistent_db");  // Error!
?>

<?php
// ✅ Fixed: Correct database name
$connection = mysqli_connect("localhost", "user", "pass", "existing_db");
?>

4. Missing Error Handling

<?php
// ❌ Error: No error checking
$connection = mysqli_connect("localhost", "user", "pass", "database");
$query = mysqli_query($connection, "SELECT * FROM users");  // May fail silently
?>

<?php
// ✅ Fixed: Proper error handling
$connection = mysqli_connect("localhost", "user", "pass", "database");
if (!$connection) {
    die("Connection failed: " . mysqli_connect_error());
}
$query = mysqli_query($connection, "SELECT * FROM users");
?>

5. Port Specification

<?php
// ❌ Error: Wrong port assumed
$connection = mysqli_connect("localhost", "user", "pass", "database");  // Uses default port
?>

<?php
// ✅ Fixed: Specify port if non-standard
$connection = mysqli_connect("localhost:3307", "user", "pass", "database");
// OR
$connection = mysqli_connect("localhost", "user", "pass", "database", 3307);
?>

6. User Permissions

<?php
// ❌ Error: User doesn't have permissions
$connection = mysqli_connect("localhost", "readonly_user", "pass", "database");  // May fail for writes
?>

<?php
// ✅ Fixed: Use user with proper permissions
$connection = mysqli_connect("localhost", "full_access_user", "pass", "database");
?>

7. Using Variables

<?php
// ❌ Error: Undefined variables
$connection = mysqli_connect($host, $username, $password, $database);  // Error!
?>

<?php
// ✅ Fixed: Define variables
$host = "localhost";
$username = "user";
$password = "pass";
$database = "database";
$connection = mysqli_connect($host, $username, $password, $database);
?>

8. Special Characters in Password

<?php
// ❌ Error: Special characters not handled
$password = "pass@word!";  // May cause issues
$connection = mysqli_connect("localhost", "user", $password, "database");
?>

<?php
// ✅ Fixed: Ensure password is properly set
$password = "pass@word!";  // Ensure no encoding issues
$connection = mysqli_connect("localhost", "user", $password, "database");
?>

9. Using MySQLi Object-Oriented Style

<?php
// ❌ Error: No error checking
$mysqli = new mysqli("localhost", "user", "pass", "database");
$query = $mysqli->query("SELECT * FROM users");  // May fail silently
?>

<?php
// ✅ Fixed: Proper error handling
$mysqli = new mysqli("localhost", "user", "pass", "database");
if ($mysqli->connect_error) {
    die("Connection failed: " . $mysqli->connect_error);
}
$query = $mysqli->query("SELECT * FROM users");
?>

10. Environment Variables

<?php
// ❌ Error: Environment not set
$connection = mysqli_connect(
    $_ENV['DB_HOST'], 
    $_ENV['DB_USER'], 
    $_ENV['DB_PASS'], 
    $_ENV['DB_NAME']
);  // Error if ENV vars not set
?>

<?php
// ✅ Fixed: Provide defaults
$connection = mysqli_connect(
    $_ENV['DB_HOST'] ?? 'localhost',
    $_ENV['DB_USER'] ?? 'user',
    $_ENV['DB_PASS'] ?? 'pass',
    $_ENV['DB_NAME'] ?? 'database'
);
?>

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Quick Debugging Steps

1. Verify credentials are correct
2. Check MySQL server is running
3. Confirm database exists
4. Test connection with MySQL client
5. Check user permissions in MySQL
6. Verify host/port are correct
7. Use error reporting: mysqli_connect_error()

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Prevention Tips

• Always check connection errors with mysqli_connect_error()
• Use environment variables for credentials
• Test database connection separately
• Verify MySQL server is running
• Ensure user has proper database permissions
• Use proper error handling in all database operations
• Check MySQL configuration for access restrictions

Remember: Verify credentials, host, database name, and user permissions to resolve access denied errors.