Why does 'method=\'post\' enctype=\'text/plain\'' cause incompatibility with PHP's $_POST array?

Unveiling the Mysteries: Understanding the Enigma of "method="post" enctype="text/plain" Incompatibility

In the realm of web development, it is often encountered that form data transmitted via POST methods may fail to reach its intended destination when the enctype attribute is set to "text/plain." Delving into the intricacies of this issue, we seek to unravel its complexities and discover the underlying cause behind this incompatibility.

Delving into the Depths: Why PHP Fails to Populate $_POST

The crux of the problem lies in PHP's inability to handle "text/plain" encoding. Despite assigning a value to the variable $HTTP_RAW_POST_DATA, PHP fails to populate the $_POST array with the form data. This is not a mere oversight but an intentional design decision.

Distinguishing GET and POST: A Tale of Encodings

It is crucial to differentiate between GET and POST methods. In GET, variables constitute the query string within the URL, necessitating URL encoding. Regardless of the enctype attribute, browsers automatically URL-encode GET variables, rendering "text/plain" ineffective.

Conversely, with POST, variables are not part of the URL but transmitted as the HTTP request's final header. Here, "text/plain" and "application/x-www-form-urlencoded" encoding options are available, but only the latter provides a non-ambiguous solution.

Ambiguity Lurks Within "text/plain": A Cautionary Tale

While "text/plain" appears to be a straightforward encoding, it harbors a hidden pitfall. It lacks mechanisms to delineate between multiple values, potentially leading to ambiguous interpretations of input data. For instance, considering 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>

If this form submits data to a PHP script expecting values for "input1" and "input2," ambiguity arises:

print($HTTP_RAW_POST_DATA);

Depending on the interpretation, the output could be:

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

Such ambiguity is absent with "application/x-www-form-urlencoded" encoding, ensuring reliable data retrieval.

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