local.ERROR: syntax error, unexpected '?', expecting variable (T_VARIABLE) - php

Question

I've uploaded my laravel 5.6 project on Ubuntu 16.04.4.
When i upload my working project(API's tested on postman) on it, it returns a blank response and on the url it states "This page isn’t working" "HTTP ERROR 500".
From what I've learnt is that the php version of my project and is different from the one on the server.
My project is built on php 7.1.9 and the server php version is 7.1.18
Any form of help or information will be useful.
Thank you in advance
Log:
local.ERROR: syntax error, unexpected '?', expecting variable (T_VARIABLE) {"exception":"[object] (Symfony\\Component\\Debug\\Exception\\FatalThr$
[stacktrace]
#0 /var/www/narcodes/vendor/composer/ClassLoader.php(322): Composer\\Autoload\\includeFile('/var/www/narcod...')
#1 [internal function]: Composer\\Autoload\\ClassLoader->loadClass('Symfony\\\\Compone...')
#2 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/RouteCompiler.php(39): spl_autoload_call('Symfony\\\\Compone...')
#3 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Route.php(284): Illuminate\\Routing\\RouteCompiler->compile()
#4 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Route.php(261): Illuminate\\Routing\\Route->compileRoute()
#5 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/RouteCollection.php(197): Illuminate\\Routing\\Route->matches(Object(Illuminate\\Http\\Request), t$
#6 [internal function]: Illuminate\\Routing\\RouteCollection->Illuminate\\Routing\\{closure}(Object(Illuminate\\Routing\\Route), 'api/user')
#7 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Support/Arr.php(175): call_user_func(Object(Closure), Object(Illuminate\\Routing\\Route), 'api/user')
#8 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Support/Collection.php(657): Illuminate\\Support\\Arr::first(Array, Object(Closure), NULL)
#9 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/RouteCollection.php(198): Illuminate\\Support\\Collection->first(Object(Closure))
#10 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/RouteCollection.php(164): Illuminate\\Routing\\RouteCollection->matchAgainstRoutes(Object(Illumin$
#11 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Router.php(619): Illuminate\\Routing\\RouteCollection->match(Object(Illuminate\\Http\\Request))
#12 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Router.php(608): Illuminate\\Routing\\Router->findRoute(Object(Illuminate\\Http\\Request))
#13 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Router.php(597): Illuminate\\Routing\\Router->dispatchToRoute(Object(Illuminate\\Http\\Request))
#14 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(176): Illuminate\\Routing\\Router->dispatch(Object(Illuminate\\Http\\Request))
#15 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(30): Illuminate\\Foundation\\Http\\Kernel->Illuminate\\Foundation\\Http\\{closure}(O$
#16 /var/www/narcodes/vendor/fideloper/proxy/src/TrustProxies.php(57): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illuminate\\Http\\Request))
#17 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(151): Fideloper\\Proxy\\TrustProxies->handle(Object(Illuminate\\Http\\Request), Obj$
#18 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(53): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illumina$
#19 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(31): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\$
#20 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(151): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle(Object(Il$
#21 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(53): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illumina$
#22 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(31): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\$
#23 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(151): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle(Object(Il$
#24 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(53): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illumina$
#25 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ValidatePostSize.php(27): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\$
#26 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(151): Illuminate\\Foundation\\Http\\Middleware\\ValidatePostSize->handle(Object(Ill$
#27 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(53): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illumina$
#28 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/CheckForMaintenanceMode.php(51): Illuminate\\Routing\\Pipeline->Illuminate\\Ro$
#29 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(151): Illuminate\\Foundation\\Http\\Middleware\\CheckForMaintenanceMode->handle(Obj$
#30 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Routing/Pipeline.php(53): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(Illumina$
#31 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(104): Illuminate\\Routing\\Pipeline->Illuminate\\Routing\\{closure}(Object(Illumina$
#32 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(151): Illuminate\\Pipeline\\Pipeline->then(Object(Closure))
#33 /var/www/narcodes/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(116): Illuminate\\Foundation\\Http\\Kernel->sendRequestThroughRouter(Object(Il$
#34 /var/www/narcodes/public/index.php(55): Illuminate\\Foundation\\Http\\Kernel->handle(Object(Illuminate\\Http\\Request))
#35 {main}
"}

Answer 1

This error is because your php server version, can be different from what you see when doing php -v.
The right way to check this is to do a php info on your server side, not on CLI.
If you need to enable php 7.2 on apache this is the command on ubuntu
first disable old php version
sudo a2dismod php7.0
enable new version
sudo a2enmod php7.2