How to Resolve \"mysqli_connect(): Parameter 6 Expected to Be a String, Resource Given\" Error in PHP SSH MySQL Connection?

Connecting to a MySQL Server over SSH in PHP

In an attempt to connect to a remote MySQL database using SSH and PHP's ssh2 library, the provided code encounters an error: "mysqli_connect() expects parameter 6 to be string, resource given." This issue arises when the parameter expected to be a string (the tunnel resource) is provided as a resource instead.

SSH Tunnel Solution

To overcome this challenge, a secure SSH tunnel can be established to connect to the MySQL database server. This tunnel acts as an encrypted channel between the client and the database, routing all communication through the secure SSH connection.

(A) GUI Tools

• Visual Studio Code: Supports SSH Tunneling with extensions.
• TablePlus: Offers built-in SSH Tunneling functionality.
• PuTTY: Allows setting up local port forwarding for SSH.

(B) Command Line

Step 1: Establish an SSH tunnel using the '-L' switch.

ssh -fNg -L 3307:10.3.1.55:3306 [email protected]

In this example, traffic on local port 3307 is forwarded to the remote database server at 10.3.1.55:3306.

Step 2: Connect to the database using the local port.

mysql -h 127.0.0.1 -P 3307 -u dbuser -p passphrase

The PHP application can now connect to the database using the SSH-forwarded connection.

<code class="php"><?php
$smysql = mysql_connect("127.0.0.1:3307", "dbuser", "passphrase");
mysql_select_db("db", $smysql);
?></code>

By setting up the SSH tunnel, the connection to the remote MySQL database becomes highly secure. Data is exchanged through the encrypted SSH channel, preventing unauthorized access.

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