Testing php / mysqli connection

Question

I am looking for a way to test just the connection portion of a php / mysqli connection. I am migrating from a LAMP server build on Vista to the same on Ubuntu and am having fits getting mysqli to work. I know that all of the proper modules are installed, and PhpMyAdmin works flawlessly. I have migrated a site over and none of the mysqli connections are working. The error that I am getting is the "call to member function xxx() on non-object" that usually pops up when either the query itself is bad or the query is prepared from a bad connection. I know that the query itself is good because it works fine on the other server with the exact same database structure and data. That leaves me with the connection. I tried to write a very simple test connection and put it in a loop such as ..

if(***connection here ***)
{ echo "connected"; }
else
{ echo "not connected"; }

It echoes "connected", which is great. But just to check I changed the password in the connection so that I knew it would not be able to connect and it still echoed "connected". So, the if / else test is clearly not the way to go....

Answer 1

mysqli_connect() always returns a MySQLi object. To check for connection errors, use:

$mysqli_connection = new MySQLi('localhost', 'user', 'pass', 'db');
if($mysqli_connection->connect_error){
   echo "Not connected, error: ".$mysqli_connection->connect_error;
}
else{
   echo "Connected."
}

Answer 2

You need more error handling on the various database calls, then. Quick/dirty method is to simply do

 $whatever = mysqli_somefunction(...) or die("MySQL error: ". mysqli_error());

All of the functions return boolean FALSE if an error occured, or an appropriate mysqli object with the results. Without the error checking, you'd be doing:

 $result = $mysqli->query("blah blah will cause a syntax error");
 $data = $result->fetchRow();  // $result is "FALSE", not a mysqli_object, hence the "call to member on non-object"