In PHP 8, error_reporting() no longer returns 0 if error suppression is enabled using @. Here is how you detect if you should respond to an error in a custom error handler.

error-handler-new.php

<?php

set_error_handler(function (int $errno, string $errstr): bool {
    if (!(error_reporting() & $errno)) {
        // Do nothing
        return false;
    }

    echo "Received error with message: $errstr\n";
    return true;
});

@trigger_error('Oops', E_USER_WARNING);