Ask the PHP operation database on the wording of the small problem

Where is the problem? I just give the $order value in the argument, I can't find the record.
But without this value, we can find 5 records.
I feel that there are some grammatical problems, please note your hand, thank you.

Reply to discussion (solution)

The order clause needs to be in front of the limit clause, and your code is in the wrong order, resulting in a syntax error. In general, limit is the last component of an SQL statement.
Incidentally, you are only discovering that you are not finding a value, and this is actually an SQL statement parsing error. If you do not know how to debug how to find the problem, then the road behind will be difficult to go

$q = ' ORDER by '. $order. ' DESC ';

You can use this method only for one table. So many fields are written dead ...
and the order by location is wrong, order by then limit

