Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in [duplicate]

Answer 1

Your second query has an SQL syntax error:

 $sql = "SELECT * FROM `apps` WHERE `MCName` = ". $username;

The $username variable needs to be wrapped in quotes. Try updating to the following to fix:

 $sql = "SELECT * FROM `apps` WHERE `MCName` = '". $username . "'";