illustrate
1. PSR-4 standardizes the specified file path to automatically load classes, and also standardizes the location of automatically loaded files.
2. Under the PSR-4 key, you can define the mapping relationship between namespace and path.
When autoloading a class like Foo\Bar\Baz, namespace Foo pointing to a directory called src/ means the autoloader will look for a file called src/Bar/Baz.php and reference it.
Example
{
"autoload": {
"psr-4": {
"App\": "App/" // Namespace App maps to directory App
}
}
}The above is the meaning of php PSR-4, I hope it will be helpful to everyone.