PHP正则表达式需要转义的字符小结
PHP正则表达式中一些需要转义的字符小结如下：
一、 $
特殊字符 注释 $ 匹配输入字符串结尾的位置。
若要匹配 $ 字符本身，请使用 \$。
二、 ( )
( ) 标记子表达式的开始和结束。可以捕获子表达式以供以后使用。
若要匹配这两个字符，请使用 \( 和 \)。
三、 *
* 零次或多次匹配前面的字符或子表达式。
若要匹配 * 字符，请使用 \*。
四、 +
+ 一次或多次匹配前面的字符或子表达式。
若要匹配 + 字符，请使用 \+。
五、 .
. 匹配除换行符 \n 之外的任何单个字符。
若要匹配 .，请使用 \。
六、 [ ]
[ ] 标记中括号表达式的开始。
若要匹配这些字符，请使用 \[ 和 \]。
七、 ?
? 零次或一次匹配前面的字符或子表达式，或指示“非贪心”限定符。
若要匹配 ? 字符，请使用 \?。
八、 \
\ 将下一字符标记为特殊字符、文本、反向引用或八进制转义符。
例如，字符 n 匹配字符 n。
\n 匹配换行符。序列 \\ 匹配 \，序列 \( 匹配 (。
九、 /
/ 表示文本正则表达式的开始或结束。
若要匹配 / 字符，请使用 \/。
十、 ^
^ 匹配输入字符串开始处的位置，但在中括号表达式中使用的情况除外，在那种情况下它对字符集求反。
若要匹配 ^ 字符本身，请使用 \^。
十一、 { }
{ } 标记限定符表达式的开始。
若要匹配这些字符，请使用 \{ 和 \}。
十二、|
| 指出在两个项之间进行选择。
若要匹配 | ，请使用 \|
\d 数字：[0-9]
\D 非数字： [^0-9]
\s 空白字符：[ \t\n\x0B\f\r]
\S 非空白字符：[^\s]
\w 单词字符：[a-zA-Z_0-9]
\W 非单词字符：[^\w]
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