Returns an associative array that corresponds to the fetched row, or false if there are no more rows.
mysql_fetch_assoc() is eqivilant to calling mysql_fetch_array() with MYSQL_ASSOC for the optional second parameter. It only returns an associative array. This is the way mysql_fetch_array() originally worked. If you need the numeric indices as well as the associative, use mysql_fetch_array().
If two or more columns of the result have the same field names, the last column will take precedence. To access the other column(s) of the same name, you must use mysql_fetch_array() and have it return the numeric indices as well.
An important thing to note is that using mysql_fetch_assoc() is NOT significantly slower than using mysql_fetch_row(), while it provides a significant added value.