Amazon GTIN Exemption: How to List Products Without a UPC, Barcode, or Product ID
Reading Time: 12 minutesAre rising GS1 barcode and UPC fees making you think twice about…
Magento 2.0 request Flow : This blog illustrates provides a full description of the Magento 2.0 code flow from index.php to .phtml file which are responsible for rendering the html. In previous articles, we have gone through simple Hello World module creation for Magento 2.0. If curious about how the output is generated or wondering what’s the code flow, then keep reading the blog till the end. 🙂
Here, will cover the main aspects of Magento’s request flow.

A quick view on how a typical web server works:
User Agent (Web browser ):
Server:
How Magento fetches output (broad view) :

Magento Request Url format :
baseurl/module front name/controller/action/parameter/value

index.php is the initial file where HTTP request to server hits, index.php further initiates Magento environment
try {
require __DIR__ . '/app/bootstrap.php';
} catch (\Exception $e) {
echo <<<HTML
<div style="font:12px/1.35em arial, helvetica, sans-serif;">
<div style="margin:0 0 25px 0; border-bottom:1px solid #ccc;">
<h3 style="margin:0;font-size:1.7em;font-weight:normal;text-transform:none;text-align:left;color:#2f2f2f;">
Autoload error</h3>
</div>
<p>{$e->getMessage()}</p>
</div>
HTML;
exit(1);
}
$bootstrap = \Magento\Framework\App\Bootstrap::create(BP, $_SERVER);
/** @var \Magento\Framework\App\Http $app */
$app = $bootstrap->createApplication('Magento\Framework\App\Http');
$bootstrap->run($app);
let’s see how it goes inside index.php line by line
1. Include Bootstrap
/**
* Environment initialization
*/
error_reporting(E_ALL);
#ini_set('display_errors', 1);
/* PHP version validation */
if (version_compare(phpversion(), '5.5.0', '<') === true) {
if (PHP_SAPI == 'cli') {
echo 'Magento supports PHP 5.5.0 or later. ' .
'Please read http://devdocs.magento.com/guides/v1.0/install-gde/system-requirements.html';
} else {
echo <<<HTML
<div style="font:12px/1.35em arial, helvetica, sans-serif;">
<p>Magento supports PHP 5.5.0 or later. Please read
<a target="_blank" href="http://devdocs.magento.com/guides/v1.0/install-gde/system-requirements.html">
Magento System Requirements</a>.
</div>
HTML;
}
exit(1);
}
As clearly visible, function version_compare checks for php version. If version found is less than 5.5.0 then it is going to throw error message and stop further execution.
/**
* Shortcut constant for the root directory
*/
define('BP', dirname(__DIR__));
$vendorDir = require BP . '/app/etc/vendor_path.php';
$vendorAutoload = BP . "/{$vendorDir}/autoload.php";
/* 'composer install' validation */
if (file_exists($vendorAutoload)) {
$composerAutoloader = include $vendorAutoload;
} else {
throw new \Exception(
'Vendor autoload is not found. Please run \'composer install\' under application root directory.'
);
}
AutoloaderRegistry::registerAutoloader(new ClassLoaderWrapper($composerAutoloader));
// Sets default autoload mappings, may be overridden in Bootstrap::create
\Magento\Framework\App\Bootstrap::populateAutoloader(BP, []);
prefixLengthsPsr4=Array(
[S] = Array(
[Symfony\CS\] = 11,
[StaticReview\] = 13,
[Seld\JsonLint\] = 14
)
[M] = Array(
[Monolog\] = 8,
[Magento\Setup\] = 14,
[Magento\Framework\] = 18,
[Magento\] = 8
)
[L] = Array(
[League\CLImate\] = 15
)
)
prefixDirsPsr4=Array(
[Symfony\CS\] = Array
(
[0] = C:\xampp\htdocs\dev\m2\vendor/fabpot/php-cs-fixer/Symfony/CS
)
[StaticReview\] = Array
(
[0] = C:\xampp\htdocs\dev\m2\vendor/sjparkinson/static-review/src
)
[Seld\JsonLint\] = Array
(
[0] = C:\xampp\htdocs\dev\m2\vendor/seld/jsonlint/src/Seld/JsonLint
)
[Monolog\] = Array
(
[0] = C:\xampp\htdocs\dev\m2\vendor/monolog/monolog/src/Monolog
)
[Magento\Setup\] = Array
(
[0] = C:\xampp\htdocs\dev\m2/setup/src/Magento/Setup
)
[Magento\Framework\] = Array
(
[0] = C:\xampp\htdocs\dev\m2/lib/internal/Magento/Framework
)
[League\CLImate\] = Array
(
[0] = C:\xampp\htdocs\dev\m2\vendor/league/climate/src
)
[Magento\] = Array
(
[0] = C:/xampp/htdocs/dev/m2/app/code/Magento/,
[1] = C:/xampp/htdocs/dev/m2/var/generation/Magento/
)
)
So how the Populate autoloader is finally set in action?
for example, if Magento requires instance of “Magento\Framework\Autoload\AutoloaderRegistry“, initially it is going to take first letter of the class Magento\Framework\Autoload\AutoloaderRegistry. The first letter is ‘M’ so it will check if prefixLengthsPsr4[‘M’] is set, in case it is not found, it will throw exception and terminate execution. Here as it’s already set then it is going to search through each entry.
Array(
[Monolog\] = 8,
[Magento\Setup\] = 14,
[Magento\Framework\] = 18,
[Magento\] = 8
)
NOTE : Don’t mind the directory separator if working in WAMP environment.
1. initially, it will search for required directory in array prefixDirsPsr4[Monolog\]]
prefixDirsPsr4 [Monolog\] = Array(
[0] = C:\xampp\htdocs\dev\m2\vendor/monolog/monolog/src/Monolog
)
it will search for file ‘AutoloaderRegistry.php‘ in directory
“C:\xampp\htdocs\dev\m2\vendor/monolog/monolog/src/Monolog”, if not found it will continue searching in the next key.
2. similarly in prefixDirsPsr4[Magento\Setup\], if is not found searches in next key.
3. searches in prefixDirsPsr4[Magento\Framework\]
prefixDirsPsr4 [Magento\Framework\] = Array(
[0] = C:\xampp\htdocs\dev\m2/lib/internal/Magento/Framework
)
if file is found in the above directory, same is returned i.e.
“C:\xampp\htdocs\dev\m2/lib/internal/Magento/Framework\Autoload\AutoloaderRegistry.php“
if (!empty($_SERVER['MAGE_PROFILER'])) {
\Magento\Framework\Profiler::applyConfig($_SERVER['MAGE_PROFILER'], BP, !empty($_REQUEST['isAjax']));
}
if (ini_get('date.timezone') == '') {
date_default_timezone_set('UTC');
}
2. Create HTTP App
/** @var \Magento\Framework\App\Http $app */
$app = $bootstrap->createApplication('Magento\Framework\App\Http');
/**
* Factory method for creating application instances
*
* @param string $type
* @param array $arguments
* @return \Magento\Framework\AppInterface
* @throws \InvalidArgumentException
*/
public function createApplication($type, $arguments = [])
{
try {
$this->initObjectManager();
$application = $this->objectManager->create($type, $arguments);
if (!($application instanceof AppInterface)) {
throw new \InvalidArgumentException("The provided class doesn't implement AppInterface: {$type}");
}
return $application;
} catch (\Exception $e) {
$this->terminate($e);
}
}
/**
* Loads the configuration file
*
* @param string $configFile
* @return array
*/
public function load($configFile = null)
{
if ($configFile) {
$file = $this->dirList->getPath(DirectoryList::CONFIG) . '/' . $configFile;
} else {
$file = $this->dirList->getPath(DirectoryList::CONFIG) . '/' . $this->file;
}
$result = @include $file;
return $result ?: [];
}
Here $configFile is set to null, hence from the else condition i.e $this->file=”config.php” it will include /app/etc/config.php in line no- 79.
3. Run App
Now run($app) function of bootstrap instance will be called.
/** @var \Magento\Framework\App\Http $app */
$app = $bootstrap->createApplication('Magento\Framework\App\Http');
$bootstrap->run($app);
/**
* Runs an application
*
* @param \Magento\Framework\AppInterface $application
* @return void
*/
public function run(AppInterface $application)
{
try {
try {
\Magento\Framework\Profiler::start('magento');
$this->initErrorHandler();
$this->initObjectManager();
$this->assertMaintenance();
$this->assertInstalled();
$response = $application->launch();
$response->sendResponse();
\Magento\Framework\Profiler::stop('magento');
} catch (\Exception $e) {
\Magento\Framework\Profiler::stop('magento');
if (!$application->catchException($this, $e)) {
throw $e;
}
}
} catch (\Exception $e) {
$this->terminate($e);
}
}
/**
* Run application
*
* @throws \InvalidArgumentException
* @return ResponseInterface
*/
public function launch()
{
$areaCode = $this->_areaList->getCodeByFrontName($this->_request->getFrontName());
$this->_state->setAreaCode($areaCode);
$this->_objectManager->configure($this->_configLoader->load($areaCode));
/** @var \Magento\Framework\App\FrontControllerInterface $frontController */
$frontController = $this->_objectManager->get('Magento\Framework\App\FrontControllerInterface');
$result = $frontController->dispatch($this->_request);
// TODO: Temporary solution till all controllers are returned not ResultInterface (MAGETWO-28359)
if ($result instanceof ResultInterface) {
$this->registry->register('use_page_cache_plugin', true, true);
$result->renderResult($this->_response);
} elseif ($result instanceof HttpInterface) {
$this->_response = $result;
} else {
throw new \InvalidArgumentException('Invalid return type');
}
// This event gives possibility to launch something before sending output (allow cookie setting)
$eventParams = ['request' => $this->_request, 'response' => $this->_response];
$this->_eventManager->dispatch('controller_front_send_response_before', $eventParams);
return $this->_response;
}
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../lib/internal/Magento/Framework/ObjectManager/etc/config.xsd">
<preference for="Psr\Log\LoggerInterface" type="Magento\Framework\Logger\Monolog" />
<preference for="Magento\Framework\View\Template\Html\MinifierInterface" type="Magento\Framework\View\Template\Html\Minifier" />
<preference for="Magento\Framework\ObjectManager\FactoryInterface" type="Magento\Framework\ObjectManager\Factory\Dynamic\Developer" />
<preference for="Magento\Framework\Search\Adapter\Mysql\Filter\PreprocessorInterface" type="Magento\Framework\Search\Adapter\Mysql\Filter\Preprocessor" />
<preference for="Magento\Framework\Search\Adapter\Mysql\Field\ResolverInterface" type="Magento\Framework\Search\Adapter\Mysql\Field\Resolver" />
<preference for="Magento\Framework\Search\Request\Aggregation\StatusInterface" type="Magento\Framework\Search\Request\Aggregation\Status" />
<preference for="Magento\Framework\App\RequestInterface" type="Magento\Framework\App\Request\Http" />
<preference for="Magento\Framework\App\Request\PathInfoProcessorInterface" type="Magento\Store\App\Request\PathInfoProcessor" />
<preference for="Magento\Framework\App\ResponseInterface" type="Magento\Framework\App\Response\Http" />
<preference for="Magento\Framework\App\RouterListInterface" type="Magento\Framework\App\RouterList" />
<preference for="Magento\Framework\App\FrontControllerInterface" type="Magento\Framework\App\FrontController" />
<preference for="Magento\Framework\App\CacheInterface" type="Magento\Framework\App\Cache\Proxy" />
<preference for="Magento\Framework\App\Cache\StateInterface" type="Magento\Framework\App\Cache\State" />
<preference for="Magento\Framework\App\Cache\TypeListInterface" type="Magento\Framework\App\Cache\TypeList" />
<preference for="Magento\Store\Model\StoreManagerInterface" type="Magento\Store\Model\StoreManager" />
<preference for="Magento\Framework\View\DesignInterface" type="Magento\Theme\Model\View\Design\Proxy" />
<preference for="Magento\Framework\View\Design\ThemeInterface" type="Magento\Theme\Model\Theme" />
<preference for="Magento\Framework\View\Design\Theme\ResolverInterface" type="Magento\Theme\Model\Theme\Resolver" />
<preference for="Magento\Framework\View\ConfigInterface" type="Magento\Framework\View\Config" />
<preference for="Magento\Framework\View\Asset\Bundle\ConfigInterface" type="\Magento\Framework\View\Asset\Bundle\Config" />
<preference for="Magento\Framework\Locale\ListsInterface" type="Magento\Framework\Locale\Lists" />
<preference for="Magento\Framework\Api\AttributeTypeResolverInterface" type="Magento\Framework\Reflection\AttributeTypeResolver" />
<type name="Magento\Store\Model\Store">
<arguments>
<argument name="currencyInstalled" xsi:type="string">system/currency/installed</argument>
</arguments>
</type>
<preference for="Magento\Framework\Locale\ConfigInterface" type="Magento\Framework\Locale\Config" />
<preference for="Magento\Framework\Notification\NotifierInterface" type="Magento\Framework\Notification\NotifierPool" />
<preference for="Magento\Framework\UrlInterface" type="Magento\Framework\Url" />
<preference for="Magento\Framework\Url\EncoderInterface" type="Magento\Framework\Url\Encoder" />
<preference for="Magento\Framework\Url\DecoderInterface" type="Magento\Framework\Url\Decoder" />
<preference for="Magento\Framework\Data\Collection\Db\FetchStrategyInterface" type="Magento\Framework\Data\Collection\Db\FetchStrategy\Query" />
<preference for="Magento\Framework\Config\ScopeInterface" type="Magento\Framework\Config\Scope" />
<preference for="Magento\Framework\Config\FileResolverInterface" type="Magento\Framework\App\Config\FileResolver" />
line number 19 : “Magento\Framework\App\FrontController” type is defined for interface “Magento\Framework\App\FrontControllerInterface“
ROUTING

Routing has an algorithm to find a matching controller, determined by request.
/**
* Route request and dispatch it
*
* @param RequestInterface $request
* @return ResponseInterface|\Magento\Framework\Controller\ResultInterface|null
*/
protected function processRequest(RequestInterface $request)
{
$result = null;
/** @var \Magento\Framework\App\RouterInterface $router */
foreach ($this->_routerList as $router) {
try {
$actionInstance = $router->match($request);
if ($actionInstance) {
$request->setDispatched(true);
$actionInstance->getResponse()->setNoCacheHeaders();
try {
$result = $actionInstance->dispatch($request);
} catch (\Magento\Framework\Exception\NotFoundException $e) {
throw $e;
} catch (\Exception $e) {
$this->handleException($e);
$result = $actionInstance->getDefaultResult();
}
break;
}
} catch (\Magento\Framework\Exception\NotFoundException $e) {
$request->initForward();
$request->setActionName('noroute');
$request->setDispatched(false);
break;
}
}
return $result;
}
line 106 : is looping routerList and extracting the required one.
<type name="Magento\Framework\App\RouterList" shared="true">
<arguments>
<argument name="routerList" xsi:type="array">
<item name="standard" xsi:type="array">
<item name="class" xsi:type="string">Magento\Framework\App\Router\Base</item>
<item name="disable" xsi:type="boolean">false</item>
<item name="sortOrder" xsi:type="string">20</item>
</item>
<item name="default" xsi:type="array">
<item name="class" xsi:type="string">Magento\Framework\App\Router\DefaultRouter</item>
<item name="disable" xsi:type="boolean">false</item>
<item name="sortOrder" xsi:type="string">100</item>
</item>
</argument>
</arguments>
</type>
Above config is adding two routers (standard and default) in routerList.
It can check Line number 20 and 25. In both, disable parameter is set to false means both are active.
Similarly you can use same method in your custom module for creating your own router.
CONTROLLER

HTTP Response
This is the end phase of magento execution where prepared output will be finally sent to requesting agent as HTTP response.
public function run(AppInterface $application)
{
try {
try {
\Magento\Framework\Profiler::start('magento');
$this->initErrorHandler();
$this->initObjectManager();
$this->assertMaintenance();
$this->assertInstalled();
$response = $application->launch();
$response->sendResponse();
\Magento\Framework\Profiler::stop('magento');
} catch (\Exception $e) {
\Magento\Framework\Profiler::stop('magento');
if (!$application->catchException($this, $e)) {
throw $e;
}
}
} catch (\Exception $e) {
$this->terminate($e);
}
}
/**
* Send content
*
* @return Response
*/
public function sendContent()
{
if ($this->contentSent()) {
return $this;
}
echo $this->getContent();
$this->contentSent = true;
return $this;
}
Line 116 : $this->getContent() finally echo/print/output the content prepared by roaming inside magento application .
If any issues / suggestion , comments are most appreciated . Next in the journey will create Products Featured Slider module in magento 2 .
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great
Thanks for appreciation
Awesome clean article on the login flow, thank you!
Is there a way to show something to screen while the page is being processed to improve the TTFB so that when going from application page to page there isnt the dreaded white screen where user is not left wondering if they pressed the wrong button ?
Hi Eibhlis,
Glad you found article interesting. Regarding your concern on TTFB and white screen get connected with our Magento experts at –
Skype – https://join.skype.com/eH1Yk2GTrVSV
Thank You!
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