Getting an error while starting Grav CMS

Getting below error while starting Grav CMS

Check write permissions

@bedoonraj, The information you've provided is not sufficient enough to pinpoint the issue.

Please provide the following information:

• when does it happen?
  • when using Admin,
  • or when using the website?
• the top 10 errors from the error logfile in /logs/grav.log
• a list of plugins you are using
• the theme you are using

@pamtbaau I'm first time downloading this tool. What i have done so far is

1. Download and Installed PHP (8.4.7)
2. Download and extracted Grav Core+Admin Plugin
3. With CMD, executed php -S localhost:8000 system/router.php

After doing i'm getting this error:

[2025-05-20 06:32:30] grav.CRITICAL: Failed to start session: session_start(): Session cannot be started after headers have already been sent - Trace: #0 C:\grav-admin\system\src\Grav\Common\Session.php(49): Grav\Framework\Session\Session->start() #1 C:\grav-admin\system\src\Grav\Common\Processors\InitializeProcessor.php(452): Grav\Common\Session->init() #2 C:\grav-admin\system\src\Grav\Common\Processors\InitializeProcessor.php(109): Grav\Common\Processors\InitializeProcessor->initializeSession(Object(Grav\Common\Config\Config)) #3 C:\grav-admin\system\src\Grav\Framework\RequestHandler\Traits\RequestHandlerTrait.php(50): Grav\Common\Processors\InitializeProcessor->process(Object(Nyholm\Psr7\ServerRequest), Object(Grav\Framework\RequestHandler\RequestHandler)) #4 C:\grav-admin\system\src\Grav\Framework\RequestHandler\Traits\RequestHandlerTrait.php(62): Grav\Framework\RequestHandler\RequestHandler->handle(Object(Nyholm\Psr7\ServerRequest)) #5 C:\grav-admin\system\src\Grav\Framework\RequestHandler\Middlewares\MultipartRequestSupport.php(40): Grav\Framework\RequestHandler\RequestHandler->handle(Object(Nyholm\Psr7\ServerRequest)) #6 C:\grav-admin\system\src\Grav\Framework\RequestHandler\Traits\RequestHandlerTrait.php(50): Grav\Framework\RequestHandler\Middlewares\MultipartRequestSupport->process(Object(Nyholm\Psr7\ServerRequest), Object(Grav\Framework\RequestHandler\RequestHandler)) #7 C:\grav-admin\system\src\Grav\Framework\RequestHandler\Traits\RequestHandlerTrait.php(62): Grav\Framework\RequestHandler\RequestHandler->handle(Object(Nyholm\Psr7\ServerRequest)) #8 C:\grav-admin\system\src\Grav\Common\Grav.php(312): Grav\Framework\RequestHandler\RequestHandler->handle(Object(Nyholm\Psr7\ServerRequest)) #9 C:\grav-admin\index.php(47): Grav\Common\Grav->process() #10 C:\grav-admin\system\router.php(55): require('C:\grav-admin\i...') #11 {main} [] []

@bedoonraj, Unfortunately, you've cross-posted this post on Gravs repo within 6 minutes apart.

In general, it is not very appreciated if users of different forums are being asked the same question. In the end, people of at least one forum are wasting time and effort.

It is OK to cross-post once the first post does not receive a proper answer. But not within 6 minutes, but after a day or so. And when cross-posting, all parties should be notified about the cross-posting and results should be shared in all forums.

I installed new version of Grav in a 8.4.7 php. Those errors are simple to correct.
In each file and line in the error message, where is:

function my_function(string $var = null){

must be in 8.4 php release:

function my_function(?string $var = null){

after corrections there is any other error, is just those simple.

@cesarmarinhorj, If it were that simple, Grav 1.7.x would have been made PHP 8.4 compatible in a blink of an eye... But there is more to it, according to the lead developer:

[..] There's more than just nullable paramaters at play, there's all the library dependencies on other libraries that need to support 8.4.