使用复选框从mysql中删除多行

I've got a query that displays a table with information about a message, I also have a column that gives the option to select the messages that the user wants to delete with a checkbox, once they have ticked the messages they want to delete, they then click on a submit button which takes them to the process page where the SQL statement to delete each selected message is made; however, the statement doesn't seem to work, this is what I have so far:I've got a query that displays a table with inf