Why Does Using `enctype='text/plain'` with POST Requests Cause Problems in PHP?

"method="post" enctype="text/plain": A Compatibility Issue

When using the form element with both method="post" and enctype="text/plain", users may encounter issues with data transmission to the specified PHP file. This is because PHP does not support handling text/plain encoding for POST data.

Why is text/plain encoding problematic?

Valid values for enctype include application/x-www-form-urlencoded and multipart/form-data. The first is the default for POST requests, while the second is used when uploading files.

When text/plain encoding is used with POST, PHP stores the raw form data in the $HTTP_RAW_POST_DATA variable instead of populating the $_POST array. This can lead to inconsistencies and ambiguity in accessing form values.

Example

Consider the following form:

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

In the corresponding PHP file:

print($HTTP_RAW_POST_DATA);

Result:

input1=abc
input2=def
input2=ghi

As seen above, it's impossible to differentiate between the values of input1 and input2, as they could be either input1=abcrninput2=def, input2=ghi or input1=abc, input2=defrninput2=ghi.

Unlike POST requests, GET requests always URL-encode the query string, even if enctype="text/plain" is specified. This is because the variables are part of the URL itself.

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