$key
$key : string
Exception to be thrown when a file was not found.
This exception is thrown when a requested file cannot be located within the filesystem.
It extends the RuntimeException and implements the ExceptionInterface to provide
a consistent exception handling mechanism across the filesystem.
__construct(string $key, int $code, \Exception|null $previous = null) : mixed
Constructs a new `FileNotFoundException` instance.
| string | $key | The key (path) of the file that was not found. |
| int | $code | The exception code (default is 0). |
| \Exception|null | $previous | Optional previous exception for chaining. |