使用数组根据拥有的键查找所需值

		// 不好的
        $ceshi = 'epub';
        if ($ceshi === 'pdf') {
            $type = 'book';
        } else if ($ceshi === 'epub') {
            $type = 'book';
        } else if ($ceshi === 'license') {
            $type = 'license';
        } else if ($ceshi === 'artwork') {
            $type = 'creative';
        } else if ($ceshi === 'song') {
            $type = 'creative';
        } else if ($ceshi === 'physical') {
            $type = 'physical';
        }        
		dd($type);

		// 推荐的
		$ceshi = 'epub';
		$type = [
            'pdf'      => 'book',
            'epub'     => 'book',
            'license'  => 'license',
            'artwork'  => 'creative',
            'song'     => 'creative',
            'physical' => 'physical',
        ][$ceshi];
        dd($type);