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php 单双引号的差异

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Jun 13, 2016 pm 12:15 PM

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php 单双引号的区别

在PHP中，字符串的定义可以使用英文单引号' '，也可以使用英文双引号" "。

但是必须使用同一种单或双引号来定义字符串，如：'Hello World"和"Hello World'为非法的字符串定义。

单引号和双引号到底有啥区别呢？

PHP允许我们在双引号串中直接包含字串变量。

而单引号串中的内容总被认为是普通字符，因此单引号中的内容不会被转义效率更高。

比如：

<span style="font-size: 13px;">$str='hello';echo "str is $str"; //运行结果: str is helloecho 'str is $str'; //运行结果: str is $str</span><br /><br /><span style="font-size: 13px;">php中，双引号中的变量($var)和特殊字符(\r\n之类)会被转义，单引号中的内容不会被转义（所以效率更高）。</span><br /><span style="font-size: 13px;">使用上的话，</span><br /><span style="font-size: 13px;">我以前很喜欢在sql字符串里这样写$sql = "SELECT * FROM table WHERE id = $id"，这样里面的$id可以被转义，单引号就不行。</span><br /><br /><span style="font-size: 13px;">在JavaScript中 单引号 和双引号没有区别，只要成对使用就行。<br />我在JavaScript 中使用单引号大多是因为 Javascript 和 HTML 打交道比较多，输出 HTML 片段的时候不需要转义 HTML 中属性的引号。<br />总之，看实际情况来用啦，怎么方便怎么使用。<br /></span><br /><br /><br /><br /><br />

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