because the values of your INSERT
statement were wrap with backticks. It should be single quote. Backticks are identifier, single quote are for string.
mysql_query("INSERT INTO `images-table` (`file-name`, `file-type`)
VALUES ('". $filename . "', '" . $type . "')");
As a sidenote, the query is vulnerable with SQL Injection
if the value(s) of the variables came from the outside. Please take a look at the article below to learn how to prevent from it. By using PreparedStatements
you can get rid of using single quotes around values.
Others