Retrieves the number of rows from a result set. This command is only valid for statements like SELECT or SHOW that return an actual result set. To retrieve the number of rows affected by a INSERT, UPDATE, REPLACE or DELETE query, use mysql_affected_rows.
The result resource that is being evaluated. This result comes from a call to mysql_query.
The number of rows in a result set on success or false on failure.
If you use mysql_unbuffered_query, mysql_num_rows will not return the correct value until all the rows in the result set have been retrieved.
For backward compatibility, the following deprecated alias may be used: mysql_numrows