stolen from Form Data Encoding Roundup :
text/plain:
Code:
Content-Type: text/plain
================================================================================
foo=bar
baz=The first line.
The second line.
application/x-www-form-urlencoded:
Code:
Content-Type: application/x-www-form-urlencoded
================================================================================
foo=bar&baz=The+first+line.%0D%0AThe+second+line.%0D%0A
multipart/form-data:
Code:
Content-Type: multipart/form-data; boundary=---------------------------314911788813839
================================================================================
-----------------------------314911788813839
Content-Disposition: form-data; name="foo"
bar
-----------------------------314911788813839
Content-Disposition: form-data; name="baz"
The first line.
The second line.
-----------------------------314911788813839--
you can see how the first one is useful for passing values UNCHECKED directly into an email program (e.g. if your form uses a mailto: address, so it uses your visitor's email program to send) but is largely useless for programmatic access to fields. only the bottom 2 examples are valid for actual form-based form data