if you want to insert a blank row ...then just make an insert statement with no walues ..
mysl_query("insert into your_table values('','','','')");
this example it's creating a new row where the row has 4 columns ... if your row has a different number of columns, just cut or add a new pair of simple quotes ... and make sure each pair is separated with - , - ... and take care about the columns delcared as "NOT NULL" which have to be filled with something.