i am editing my question.what is the valid php version for laravel 5.3 becuase if i change it to 7.0 and 5.6 it starts showing a white blank page.and in the error logs it showsphp version error.and when i change it back to 5.5 website shows a 500 error and logs says permission error which i have already changed to (755).can't get over it.
To find valid php versions, look at composer.json that comes with laravel. It will say something like:
"php": ">=5.6.4", in the require section (that is for laravel 5.4, not 5.3)
That section will also tell you what php modules are required, like: