这个正则中的x7f-xff是什么意思-PHP Tutorial-php.cn

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这个正则中的x7f-xff是什么意思

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Jun 23, 2016 pm 02:38 PM

看到一个源码中写的正则里
/\/i

中的 \x7f-xff代表什么意思

回复讨论(解决方案)

\x7f-\xff表示ASCII字符从127到255，其中\为转义。

这里为什么要从127到255这个范围取值呢？不好意思，再深入的问一下。

echo bin2hex('为什么'); //得 ceaacab2c3b4

echo "\xce\xaa\xca\xb2\xc3\xb4"; //得为什么

这里为什么要从127到255这个范围取值呢？不好意思，再深入的问一下。

可能是IP地址分类吧
A：首位为0；1.0.0.0~126.0.0.0；主机号24位
B：前两位为10；128.1.0.0~191.255.0.0；主机号16位
C：前三位为110；192.0.1.0~223.255.255.0；主机号8位
D：前四位为1110；224.0.0.0~239.255.255.255
E：前四位为1111；240.0.0.0~255.255.255.254

！！！这个和IP有什么关系！！！

在中括号中除了中括号本身或连接符表示范围的时候，其他情况都不是元字符。所以[\x7f-xff]代表\、x、7、f-x、f、f的字符组。

不好意思，昨天的回复是错误的，更正一下，元字符“\xn”用于匹配n，其中n为十六进制转义值，该值必须为确定的两个数字长。例如，“\x41”匹配“A”，“\x411”则等价于“A1”。而连接符“-”在字符组（中括号内的字符串）内表示一个范围（如果不在开头）。值得注意的是，在字符组内部和外部，关于元字符的规定是不同的。

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