第一篇博文：PHP函数原型中的可选参数写法为何这么写-PHP Tutorial-php.cn

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第一篇博文：PHP函数原型中的可选参数写法为何这么写

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Jun 13, 2016 pm 12:23 PM

explodelimitstring

第一篇博文：PHP函数原型中的可选参数写法为什么这么写？

第一篇，算是开始吧。简单写点儿东西。

刚开始学PHP，在看PHP Manual时遇到一个问题：含可选参数的函数原型中，可选参数的写法看不懂。

例如explode函数

<span style="font-size: 14px;">array explode ( string $delimiter , string $string [, int $limit ] )</span>

可选参数都用“[方括号]”括起来，那么第三个参数$limit为可选参数。

可是为什么不这么写呢：

<span style="font-size: 14px;">array explode ( string $delimiter , string $string ,[int $limit ] )</span>

实在是无法理解这个逗号的位置。

1楼DeanChopper: 可选指的是[]内的东西可有可无而不是参数，所以按你的方式无论有没有最后的参数第二个参数后面都有一个,显然这是不行的

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