WE can get the number of fields in our executed query by using mysql_num_fields function. This function returns the number of fields returned by the query.
Here is an example
$query="select * from student";
$result=mysql_query($query);
$fields=mysql_num_fields($result);
echo $fields;
The above code will print 4 as we have 4 columns in our student table.
Now let us change the query a bit ( only query part is changed and all other parts remain same )
$query="select name,id from student";
Now the output of the print command will display 2 ( not 4 ). So the function mysql_num_fields function returns the number of columns returned by the query.