PHP属于解析型语言,请问以下语句性能上有什么区别吗?
<code># 使用if进行判断 if( !defined('ROOT_PATH') ) define('ROOT_PATH', realpath('./').DIRECTORY_SEPARATOR); # 使用or进行判断 defined('ROOT_PATH') or define('ROOT_PATH', realpath('./').DIRECTORY_SEPARATOR); !defined('ROOT_PATH') and define('ROOT_PATH', realpath('./').DIRECTORY_SEPARATOR); </code>
回复内容:
<code># 使用if进行判断 if( !defined('ROOT_PATH') ) define('ROOT_PATH', realpath('./').DIRECTORY_SEPARATOR); # 使用or进行判断 defined('ROOT_PATH') or define('ROOT_PATH', realpath('./').DIRECTORY_SEPARATOR); !defined('ROOT_PATH') and define('ROOT_PATH', realpath('./').DIRECTORY_SEPARATOR); </code>
if
效率要比短路
写法效率高,因为if
只需要判断if
括号里的条件是否为真,如果为真,直接执行条件里的代码,不管里面代码返回的是真是假。而or
或者and
在执行后面代码后,会判断返回值是否为真。
个人表示,性能上没有区别
都是1次判断或者1次判断+定义
自己测试一下不就知道了
<code> (1==1) || print(2); (1==1) && print(2); </code>
结果显示,如果是或,第一个为真,则不会运行后面的表达式,如果第一个为假,则会运行
如果是与,如果第一个为假,则不会运行后面的表达式,否则则运行
所以跟if的效果是一样的,而且写法更简洁,尤其适合开始的预定义
if里只有一次计算。

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