/**
* @param WindConnection $connection WindConnection对象
* @param string $query 预定义语句
*/
public function __construct($connection = null, $query = '') {
$connection && $this->_connection = $connection;
$query && $this->setQueryString($query);
}什么意思?$connection && $this->_connection = $connection;
* @param WindConnection $connection WindConnection对象
* @param string $query 预定义语句
*/
public function __construct($connection = null, $query = '') {
$connection && $this->_connection = $connection;
$query && $this->setQueryString($query);
}什么意思?$connection && $this->_connection = $connection;
if( $connection && $this->_connection = $connection )
当 && 前的表达式结果为true时,则需要执行第二个表达式来确定条件成立
但当 $connection 为false时,就没有必要执行第二个表示了,因为条件已经确立为不成立
等价于
if($connection){
$this->_connection = $connection;
}
$connection && $this->_connection = $connection;!empty($connection) && $this->_connection = $connection;相当于
if(!empty($connection))$this->_connection = $connection;
为什么一个定义成空,一个定义成 null,有什么区别吗