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Home Backend Development PHP Tutorial PHP属于解析型语言,请问以下语句性能上有什么区别吗?

PHP属于解析型语言,请问以下语句性能上有什么区别吗?

Jun 06, 2016 pm 08:37 PM
php

<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>
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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>
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Copy after login

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>
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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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