Han shunping: Regular Expression exercise questions

The following are the expressions used by Han shunzheng to exercise questions. I hope to help students of php Chinese network!

The following is an expression Exercise by Han shun Zheng, hoping to help students in the first PHP community!

Question 1: understanding of m in the matching option gim, ^ (\ d) u $

2 Aaaddddjkkkkku

4 ddddkkiieu

Effect of ^ in Multi-section mode on positioning at the beginning and end

Question 2: Give the matching result:

/(\ D) {4}/gi match AAA1234kkkk

/1 {3}/1111 111 appears several times 111 2 times

/1 {3, 4}/1111 111 appears several times 1111,111 note greedy match once 1111 once 111

/1 +/1111 111 the result is a greedy match of 1111 111

/1 */1111 111 the result is 11111111 at a time

/1? /The result of null character match is successful.

The/a1 */a111111 result is a111111. Note that * is modified by 1.

[Abc] abcd matches a, B, c, d in sequence.

/(Han | inclusive)/select a match character

Question 3: Construct a regular expression () of a rule called a subexpression.

Abba (\ d) \ 2 \ 1 Note \ 1 is not (\ d) Learn to capture subexpressions and reverse reference subexpressions

For example, aabbccdd (\ d) \ 1 (\ d) \ 2 (\ d) \ 3 (\ d) \ 4

The first five digits are any number-339911 (\ d) {5}-(\ d) \ 2 (\ d) \ 3 (\ d) \ 4

Comprehensive: email format

1. Only one @

2. @ the front is the user name, can be 0-9 a-z A-Z _ character

3. @ is followed by a domain name, which can be sohu.com or tsinghua.org.cn and can only contain English letters.

/^ [A-zA-Z0-9 _-] + @ ([a-zA-Z0-9 _-] + \.) + (com | cn | net | org) $/