Why are PHP POST variables missing from $_POST despite being present in php://input?

PHP POST Variables Missing Despite Presence in php://input

Introduction:

When processing form submissions in PHP via POST requests, it's possible to encounter a strange behavior where certain values are absent in the $_POST superglobal even though they are present in the raw request via php://input.

Problem Description:

The issue arises when submitting large HTML forms with nested fields. Despite the form data being sent to the server, some values may fail to populate in $_POST. Inspection of php://input reveals that these values are indeed included in the request but appear to be truncated in $_POST.

Cause:

The behavior is attributed to PHP's modification of POST fields containing characters like dots, spaces, open square brackets, etc. These characters were previously processed by the deprecated register_globals configuration.

Solution:

To address this issue, you can employ workarounds such as the following:

<code class="php">// Get real POST variables
function getRealPOST() {
    $pairs = explode("&", file_get_contents("php://input"));
    $vars = array();
    foreach ($pairs as $pair) {
        $nv = explode("=", $pair);
        $name = urldecode($nv[0]);
        $value = urldecode($nv[1]);
        $vars[$name] = $value;
    }
    return $vars;
}</code>

This function parses the raw POST request in php://input and reconstructs the POST variables with the original field names, accounting for the character replacements made by PHP.

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