Error Ketika Menjalankan Perintah "php artisan serve"

PROBLEM

Terjadi error seperti ini ketika menjalankan perintah "php artisan serve".

PHP Warning: require(C:\xampp\htdocs\boardingschool\bootstrap/../vendor/autoloa
d.php): failed to open stream: No such file or directory in C:\xampp\htdocs\boar
dingschool\bootstrap\autoload.php on line 17

Warning: require(C:\xampp\htdocs\boardingschool\bootstrap/../vendor/autoload.php
): failed to open stream: No such file or directory in C:\xampp\htdocs\boardings
chool\bootstrap\autoload.php on line 17
PHP Fatal error: require(): Failed opening required 'C:\xampp\htdocs\boardingsc
hool\bootstrap/../vendor/autoload.php' (include_path='C:\xampp\php\PEAR') in C:\
xampp\htdocs\boardingschool\bootstrap\autoload.php on line 17

Fatal error: require(): Failed opening required 'C:\xampp\htdocs\boardingschool\
bootstrap/../vendor/autoload.php' (include_path='C:\xampp\php\PEAR') in C:\xampp
\htdocs\boardingschool\bootstrap\autoload.php on line 17