Can MySQL's `mysql_` and `mysqli_` APIs Be Used Together in PHP?

Can MySQL APIs Be Mixed in PHP?

Mixing MySQL APIs in PHP is not recommended. PHP provides two MySQL API extensions: mysql_ and mysqli_. These extensions are separate and their resources are incompatible.

The code you provided demonstrates the issue:

$con = mysqli_connect("localhost", "root" ,"" ,"mysql");

if( mysqli_connect_errno( $con ) ) {
    echo "failed to connect";
}else{
    echo "connected";
}

mysql_close($con);
echo "Done";

This code results in the following error:

Connected
Warning: mysql_close() expects parameter 1 to be resource, object given in D:\************.php on line 9
Done

This error occurs because mysql_close() expects a MySQL resource as input, but you are providing a mysqli resource.

Solution:

To resolve this issue, use only one MySQL API extension consistently throughout your code. If you are using the mysqli_ extension, use mysqli_connect() and mysqli_close() to open and close the connection. Similarly, if you are using the mysql_ extension, use mysql_connect() and mysql_close().

Checking Connection Validity:

Both mysql_connect_errno() and mysqli_connect_errno() can be used to check if the connection is valid. If the returned value is 0, the connection is valid. Otherwise, there is an error.

Example:

$con = mysqli_connect("localhost", "root" ,"" ,"mysql");

if( mysqli_connect_errno( $con ) ) {
    echo "failed to connect: " . mysqli_connect_error();
}else{
    echo "connected";
}

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