I suspect gremlins. I've got a simplest MySQL query
$toProcess = mysql_query("SELECT * FROM url_list ORDER BY id DESC LIMIT 7 WHERE type='get'");
The first time I ran the test script I got a blank screen.
Then I hit F5 and got a Syntax error message suggesting that I have to consult the manual and check for errors around WHERE type='get'
I hit F5 again and I got a blank screen again.
Unless both the MySQL manual and W3schools tutorial are wrong, there is no syntax error in my query.