Why Is Composer Install Not Working On Cent Os6?

I downloaded a laravel project with git in cent os6, and as I try to do "composer install" I get a folloing error.

[RuntimeException]
/var/www/laracms/vendor does not exist and could not be created.

I gave a writing permission to composer by typing

sudo chmod +x /usr/local/bin/composer

I expected the error to be solved, but it did not work. I even changed the permission of "var/www/" and it did not work either. Can someone help me???

rw-r--r--. 1 root root      348 Aug  8 16:17 additional-supervisord.conf
drwxr-xr-x. 7 root root     4096 Aug  8 16:17 app
-rw-r--r--. 1 root root     1409 Aug  8 16:17 app.yaml
-rw-r--r--. 1 root root     1686 Aug  8 16:17 artisan
drwxr-xr-x. 3 root root     4096 Aug  8 16:17 bootstrap
-rwxr-xr-x. 1 root root 12886152 Aug  8 16:17 cloud_sql_proxy
-rw-r--r--. 1 root root     1925 Aug  8 16:17 composer.json
-rw-r--r--. 1 root root   216426 Aug  8 16:17 composer.lock
drwxr-xr-x. 2 root root     4096 Aug  8 16:17 config
drwxr-xr-x. 5 root root     4096 Aug  8 16:17 database
-rw-r--r--. 1 root root     1125 Aug  8 16:17 package.json
-rw-r--r--. 1 root root      220 Aug  8 16:17 php.ini
-rw-r--r--. 1 root root     1156 Aug  8 16:17 phpunit.xml
drwxr-xr-x. 5 root root     4096 Aug  8 16:17 public
drwxr-xr-x. 6 root root     4096 Aug  8 16:17 resources
drwxr-xr-x. 2 root root     4096 Aug  8 16:17 routes
-rw-r--r--. 1 root root      563 Aug  8 16:17 server.php
drwxr-xr-x. 5 root root     4096 Aug  8 16:17 storage
drwxr-xr-x. 4 root root     4096 Aug  8 16:17 tests
-rw-r--r--. 1 root root      538 Aug  8 16:17 webpack.mix.js
-rw-r--r--. 1 root root   201370 Aug  8 16:17 yarn.lock

It's in /var/www/laracms directory that the permission problem resides.

It looks like you've downloaded the laravel project as root. To get you started you could do 'sudo composer install'. Not sure if root ownership of your files served by your web server is what you want.