A tray inside a tray

1<?php2class SaveFailed extends Exception {}3function write(): void {4    throw new RuntimeException('disk full');5}6function save(): void {7    try {8        write();9    } catch (RuntimeException $e) {10        echo "save logs: ", $e->getMessage(), "\n";11        throw new SaveFailed('could not save', 0, $e);12    }13}14try {15    save();16} catch (SaveFailed $e) {17    echo $e->getMessage(), "\n";18    echo "because: ", $e->getPrevious()->getMessage(), "\n";19}