    use Eno2050\Phptools\Traits\Singleton;

    class user {
        use Singleton;
        public function sayHello(){
            return 'hello world';
        }
    }
    
    $user = User::getInstance();
    echo $user->sayHello();

arrayTools 数组工具类

changeKeyCase

	@param array $arr 要转换的数组
	@param boolean $flag 默认true 转换成大写
	@return array
	public function changeKeyCase(array $arr, $flag = true);