Warning: require(vendor/autoload.php): Failed to open stream: No such file or directory in C:\xampp\htdocs\www_real\retorno.php on line 2

Fatal error: Uncaught Error: Failed opening required 'vendor/autoload.php' (include_path='C:\xampp\php\PEAR') in C:\xampp\htdocs\www_real\retorno.php:2 Stack trace: #0 {main} thrown in C:\xampp\htdocs\www_real\retorno.php on line 2