How do you mean by 'mode'? Actually to modify row(s) in database (i presume you are using mysql), you just need to prepare a update statement and execute with a php function mysql_query(). If you are not known to the update statement it looks like this.
$id = 10;// this value can be dynamic by passing from query string or form
$sql = "UPDATE tblname SET columname='NewValue', columnname2='NewValue' WHERE id=$id";
mysql_query($sql) or die(mysql_error());
This will update a single record in the table. Where clause will determine what rows to update and you can put various number of columns.