Just another weird PHP function
github.com
github.com
Also, the mysqli extension should be preferred over mysql so it should come before in the code.
Finally, if your connection fails, $dbconn will be set to false, which is == to null in PHP. You should have two checks on this variable: $dbcon === NULL and $dbconn === false.
And seriously, what are the chances of having the mysqli stuff but not the mysql_* functions?