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HomeBackend DevelopmentPHP TutorialPHP5.5和之前的版本empty函数的不同之处_php技巧

作为我最喜欢使用的函数之一,今天也终于发现这个函数的恶魔之处。洋洋洒洒写了以下代码,本地测试一切ok,到服务器上就SB了。

复制代码 代码如下:

if(strlen($passwd)     //do something
}

大致的意思就是,密码必须大于6位切不能只由数字组成。找遍服务器日志,发现如下错误:
复制代码 代码如下:

PHP Fatal error: Can't use function return value in write context in /xxx/xxx/xx.php on line xxx

google了一下,大概是说,empty的参数不能为函数。我靠,本地明明是好的。看了下本地的PHP是5.5的,服务器是5.3的。难道这函数在2个版本之间就进化了么?找遍了PHP官方的文档没有发现任何端倪,然后google狂搜,不小心点到了PHP英文文档界面,在empty函数的介绍下面,发现了一行小字:

复制代码 代码如下:

Note:
Prior to PHP 5.5, empty() only supports variables; anything else will result in a parse error. In other words, the following will not work: empty(trim($name)). Instead, use trim($name) == false.

恶魔啊,不带这么坑中文用户的。总结下empty函数的使用场景:

1.PHP 5.5之前的版本,这个函数是用来检查变量的赋值是否为0, false, 空字符串, null。任何非变量形式的参数都是导致这个函数报错。
2.PHP 5.5这个函数可以应用于任何值,而不局限于变量。可以为常量、函数返回值等等。

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