Why is `enctype='text/plain'` incompatible with the POST method in HTML forms?

Why is "method="post" enctype="text/plain"" not compatible?

When using the HTML form encoding method "post" with "enctype="text/plain"," form data fails to be delivered to the PHP script. What is the reason behind this issue? Why is text/plain encoding incompatible with post while it is allowed with get?

Explanation

PHP does not support "enctype="text/plain"" for "method="post"; it is not a program bug.

Approved values for "enctype" in a form are:

• application/x-www-form-urlencoded
• multipart/form-data

The first option is the default, while the second is essential for file uploads.

PHP does not populate the $_POST array when "enctype="text/plain"" is used; instead, it stores the value in $HTTP_RAW_POST_DATA.

Potential Issues with Text/Plain Encoding

Consider the following scenario:

In file1.php:

<form method="post" enctype="text/plain" action="file2.php">
  <textarea name="input1">abc
input2=def</textarea>
  <input name="input2" value="ghi" />
  <input type="submit">
</form>

In file2.php:

<?php
print($HTTP_RAW_POST_DATA);
?>

The expected result:

input1=abc
input2=def
input2=ghi

However, with text/plain encoding, there is no way to distinguish the values of input1 and input2. The result could be:

• input1=abcrninput2=def, input2=ghi
• input1=abc, input2=defrninput2=ghi

The difference between GET and POST is that:

• GET variables appear in the URL as query strings and must be URL-encoded, even with enctype="text/plain."
• POST variables are transmitted in the HTTP request's final header (POSTDATA), allowing for encoding as either text/plain or application/x-www-form-urlencoded. However, the latter is preferred to avoid ambiguity.

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