Guzzle 6, get request string

According to a comment in this github issue, you can use the history middleware to store/output the request/response info.

use GuzzleHttp\Client;
use GuzzleHttp\HandlerStack;
use GuzzleHttp\Middleware;

$container = [];
$history = Middleware::history($container);

$stack = HandlerStack::create();
// Add the history middleware to the handler stack.
$stack->push($history);

$client = new Client(['handler' => $stack]);

$client->request('POST', 'http://httpbin.org/post',[
    'body' => 'Hello World'
]);

// Iterate over the requests and responses
foreach ($container as $transaction) {
    echo (string) $transaction['request']->getBody(); // Hello World
}

A more advanced example here: http://docs.guzzlephp.org/en/stable/testing.html#history-middleware

use GuzzleHttp\Client;
use GuzzleHttp\HandlerStack;
use GuzzleHttp\Middleware;

$container = [];
$history = Middleware::history($container);

$stack = HandlerStack::create();
// Add the history middleware to the handler stack.
$stack->push($history);

$client = new Client(['handler' => $stack]);

$client->request('GET', 'http://httpbin.org/get');
$client->request('HEAD', 'http://httpbin.org/get');

// Count the number of transactions
echo count($container);
//> 2

// Iterate over the requests and responses
foreach ($container as $transaction) {
    echo $transaction['request']->getMethod();
    //> GET, HEAD
    if ($transaction['response']) {
        echo $transaction['response']->getStatusCode();
        //> 200, 200
    } elseif ($transaction['error']) {
        echo $transaction['error'];
        //> exception
    }
    var_dump($transaction['options']);
    //> dumps the request options of the sent request.
}

As per Guzzle documentation there is debug option, here is the link from guzzle documentation http://guzzle.readthedocs.org/en/latest/request-options.html#debug

$client->request('GET', '/get', ['debug' => true]);

Mohammed Safeer's answer is the correct one, but to make it easier for folks who just set debug to true and got a bunch of text rendered in the middle of their script execution, you can also do the following:

$debug = fopen("path_and_filename.txt", "a+");
$client->request('GET', '/get', ['debug' => $debug ]);

This will output the debugging steam to a given file and not "interrupt" the execution of the request.