详解两个PHP正则表达式特殊字符
PHP正则表达式特殊字符"[ ]"和""，那么他们是什么呢？具体的操作是什么呢？之所以他们是特殊字符，那么有什么在使用过程中特别的地方么？来让我们看看具体的介绍。
还有两个很重要的特殊字符就是"[ ]"。他们可以匹配"[]"之中出现过的字符，比如"/[az]/"可以匹配单个字符"a"或者"z"；如果把上面的表达式改成这样"/[a-z]/"，就可以匹配任何单个小写字母，比如"a"、"b"等等。
关于PHP正则表达式特殊字符"[ ]"：
如果在"[]"中出现了"^"，代表本表达式不匹配"[]"内出现的字符，比如"/[^a-z]/"不匹配任何小写字母！并且正则表达式给出了几种"[]"的默认值：
◆[:alpha:]：匹配任何字母
◆[:alnum:]：匹配任何字母和数字
◆[:digit:]：匹配任何数字
◆[:space:]：匹配空格符
◆[:upper:]：匹配任何大写字母
◆[:lower:]：匹配任何小写字母
◆[:punct:]：匹配任何标点符号
◆[:xdigit:]：匹配任何16进制数字
关于PHP正则表达式特殊字符""：
下面这些特殊字符在转义符号""转义后代表的含义如下：
◆s：匹配单个的空格符
◆S：用于匹配除单个空格符之外的所有字符。
◆d：用于匹配从0到9的数字，相当于"/[0-9]/"。
◆w：用于匹配字母，数字或下划线字符，相当于"/[a-zA-Z0-9_]/"。
◆W：用于匹配所有与w不匹配的字符，相当于"/[^a-zA-Z0-9_]/"。
◆D：用于匹配任何非10进制的数字字符。
.◆：用于匹配除换行符之外的所有字符，如果经过修饰符"s"的修饰，"."可以代表任意字符。
关于PHP正则表达式特殊字符的介绍就向你介绍到这里，希望那个对你了解和掌握PHP正则表达式特殊字符的使用有所帮助。
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