php://input can only be read once in PHP 5.6.16

PHP manual states that a stream opened with php://input support seek operation and can be read multiple times as of PHP 5.6, but I can't make it work. The following example clearly shows it doesn't work:

<!DOCTYPE html>
<html>
<body>
<form method="post">
<input type="hidden" name="test_name" value="test_value">
<input type="submit">
</form>
<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST')
{
    $input = fopen('php://input', 'r');
    echo 'First attempt: ' . fread($input, 1024) . '<br>';
    if (fseek($input, 0) != 0)
        exit('Seek failed');
    echo 'Second attempt: ' . fread($input, 1024) . '<br>';
}
?>
</body>
</html>

Output:

First attempt: test_name=test_value
Second attempt:

php://input stream was

successfully read
successfully rewinded (fseek succeeded)
unsuccessfully read

Am I doing something wrong?

Solution

With the amount of exceptions and lack of portability using php://input I'd recommend you to read the stream and save it to another stream to avoid unexpected behaviour.

You can use php://memory in order to create a file-stream-like wrapper, which will give you all the same functionality that php://input should have without all of the annoying behaviour.

Example:

<?php

$inputHandle = fopen('php://memory', 'r+');

fwrite($inputHandle, file_get_contents('php://input'));

fseek($inputHandle, 0);

Additionally you can create your own class to refer to this object consistently:

<?php

class InputReader {
    private static $instance;

    /**
     * Factory for InputReader
     *
     * @param string $inputContents
     *
     * @return InputReader
     */
    public static function instance($inputContents = null) {
        if (self::$instance === null) {
            self::$instance = new InputReader($inputContents);
        }

        return self::$instance;
    }

    protected $handle;

    /**
     * InputReader constructor.
     *
     * @param string $inputContents
     */
    public function __construct($inputContents = null) {
        // Open up a new memory handle
        $this->handle = fopen('php://memory', 'r+');

        // If we haven't specified the input contents (in case you're reading it from somewhere else like a framework), then we'll read it again
        if ($inputContents === null) {
            $inputContents = file_get_contents('php://input');
        }

        // Write all the contents of php://input to our memory handle
        fwrite($this->handle, $inputContents);

        // Seek back to the start if we're reading anything
        fseek($this->handle, 0);
    }

    public function getHandle() {
        return $this->handle;
    }

    /**
     * Wrapper for fseek
     *
     * @param int $offset
     * @param int $whence
     *
     * @return InputReader
     *
     * @throws \Exception
     */
    public function seek($offset, $whence = SEEK_SET) {
        if (fseek($this->handle, $offset, $whence) !== 0) {
            throw new \Exception('Could not use fseek on memory handle');
        }

        return $this;
    }

    public function read($length) {
        $read = fread($this->handle, $length);

        if ($read === false) {
            throw new \Exception('Could not use fread on memory handle');
        }

        return $read;
    }

    public function readAll($buffer = 8192) {
        $reader = '';

        $this->seek(0); // make sure we start by seeking to offset 0

        while (!$this->eof()) {
            $reader .= $this->read($buffer);
        }

        return $reader;
    }

    public function eof() {
        return feof($this->handle);
    }
}

Usage:

$first1024Bytes = InputReader::instance()->seek(0)->read(1024);
$next1024Bytes = InputReader::instance()->read(1024);

Usage (read all):

$phpInput = InputReader::instance()->readAll();