Warning: require(vendor/autoload.php): failed to open stream: No such file or directory in /index.php on line 4

Warning: require(vendor/autoload.php): failed to open stream: No such file or directory in /index.php on line 4

Fatal error: require(): Failed opening required 'vendor/autoload.php' (include_path='.:/:/usr/local/php55/lib/pear') in /index.php on line 4