韩顺平：正则表达式练习题
以下是韩顺平正则表达式练习题，希望对php中文网的同学们有帮助！
问题1：匹配选项 gim 中对m的理解， ^(\d) u$
2Aaaddddjkkkkku
4ddddkkiieu
在多段落模式下^ ,对开头 结尾定位的影响
问题2：说出一下匹配的结果：
/(\d){4}/gi 匹配 AAA1234kkkk
/1{3}/ 1111 111 出现几次111 2次
/1{3,4}/ 1111 111 出现几次1111， 111 注意贪婪匹配 一次1111 一次111
/1+/ 1111 111 结果是 注意贪婪匹配 一次1111 111
/1*/ 1111 111 结果是 一次11111111
/1?/ 空字符 结果是 出现空字符匹配成功
/a1*/ a111111 结果是 a111111 注意*是修饰1的
[abc] abcd 依次匹配到 a,b,c,d
/(han|韩|含)/ 选择匹配符
问题3：构造一下规则的正则表达式 ()叫做子表达式
abba (\d)(\d)\2\1 注意\1不是(\d) 学会捕获子表达式与反向引用子表达式
形如aabbccdd (\d)\1(\d)\2(\d)\3(\d)\4
前5位为任意数-339911 (\d){5}-(\d)\2(\d)\3(\d)\4
综合：电子邮件格式
1.只有一个@
2.@前面是用户名，可以是0-9 a-z A-Z _字符
3.@后面是域名，可以是sohu.com 或tsinghua.org.cn并且域名只能是英文字母
/^[a-zA-Z0-9_-]+@([a-zA-Z0-9_-]+\.)+(com|cn|net|org)$/
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