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Q:

mysql - PHP undefined variable mysqli connection

Hey everyone,

I'm facing an issue with my MySQL and PHP code. I keep getting an "undefined variable mysqli connection" error message, and I'm not sure how to fix it. Can anyone help me out?

Here's some background on my code:

I'm currently working on a PHP project that involves connecting to a MySQL database. I've already installed PHP and MySQL on my server, and I've created a database with some tables.

To establish the connection, I have the following code snippet:

```php
<?php
$servername = "localhost";
$username = "root";
$password = "my_password";
$dbname = "my_database";

$conn = mysqli_connect($servername, $username, $password, $dbname);

if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}
?>
```

I'm trying to establish a connection to my MySQL database using the `mysqli_connect()` function. However, when I run my code, I keep getting the error message "undefined variable mysqli connection". I don't understand why this error is occurring and how to resolve it.

I have already verified that the connection details (server name, username, password, and database name) are correct. So, I'm not sure what could be causing this issue.

Has anyone encountered a similar problem before? Any insights or suggestions would be greatly appreciated.

Thanks in advance!

All Replies

caterina30

Hey there,

I faced a similar issue before, and the problem was actually with the variable scope in my code. It appeared that the error message "undefined variable mysqli connection" was caused by a typo or a missing declaration of the `$conn` variable before trying to establish the MySQLi connection.

Make sure that you have defined the `$conn` variable before using it for the connection. If you already have the variable defined correctly in your code, check if there are any typos or conflicting variable names.

Also, ensure that you're not accidentally reusing the variable name `$conn` within any functions or conditionals, as it could lead to scope issues.

Here's an example of how you can explicitly declare the `$conn` variable before establishing the connection:

php
<?php
$servername = "localhost";
$username = "root";
$password = "my_password";
$dbname = "my_database";

$conn = null; // Explicitly declare and initialize the variable

$conn = mysqli_connect($servername, $username, $password, $dbname);

if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}
?>


By explicitly initializing the `$conn` variable to `null` before the connection code, you can avoid any undefined variable issues that might occur.

Give it a try and let us know if it resolves your problem. If you're still facing any issues, provide us with more details about your code and any relevant error messages you receive so that we can further assist you.

larkin.cara

Hey there,

I had a similar issue before and it turned out that I forgot to enable the MySQLi extension in my PHP configuration file. You might want to double-check if the extension is enabled in your setup.

To do this, you can open your `php.ini` file and search for the line `extension=mysqli`. If you find a semicolon (;) in front of it, remove the semicolon to uncomment the line. Then, save the file and restart your web server.

Another thing you can try is to use the procedural style of connecting to the database instead of the object-oriented style. Here's an alternative code snippet you can give a shot:

php
<?php
$servername = "localhost";
$username = "root";
$password = "my_password";
$dbname = "my_database";

$conn = mysqli_connect($servername, $username, $password, $dbname);

if (!$conn) {
die("Connection failed: " . mysqli_connect_error());
}
?>


You can give these suggestions a try and see if they resolve your issue. If not, please provide more details about your PHP and MySQL versions, as well as any other relevant information, so that we can better assist you.

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