[Consolidating the PHP series] PHP regular expressions

【Consolidating PHP series】PHP regular expressions

1. Overview

1. Regular expression test address: http://tool.chinaz.com/regex/

2. Specific commonly used regular expressions

1. Email regular expression:
　1) w[-w.+]*@([A-Za-z0-9][-A-Za-z0-9]+.)+[A-Za- z]{2,14}
　2) w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*
　3) Analysis:

　-- " " " is called "escape character". Used to escape some special symbols, such as ".","/"

　　-- "w" Equivalent to [a-zA-Z0-9_]. Also matches Chinese characters

　　　--"+" 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　 1 to 1 or more times, can also be written as {1,}

　　　--"Parentheses" are used to specify subexpressions (also called groupings), and then you can specify the repetition of this subexpression times, ([-+.]w+)*

　　　--[-+.]　The part expanded by square brackets is the character field

　　　--.

<?php
  $email = &#39;sishuinianhua@qq.com&#39;;
  $preg = &#39;/\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*/&#39;;
  $res = preg_match($preg, $email, $preg_res);
  var_dump(111,$res,$preg_res);exit;

　--preg_match(): http://php.net/manual/zh/function.preg-match.php

2. URL expression:

　1) [a-zA-z]+:// [^s]+

　2) Analysis:

　-- ^

　　　> Put it in the character field (such as: [^w]) to express negation (meaning not to include) - "reverse selection"

　　　　　Placed before the expression, it means starting with the current character. (/^n/i, means starting with n).

　　 -- s Matches any whitespace character

3. Appendix

1. Commonly used metacharacters

Code Description

. Matches any character except line breaks

w Matches letters or numbers or underscores
s match Any whitespace character
d Matches numbers
b Matches the beginning or end of a word
^ Matches the beginning of a string
$ Matches the end of a string

2. Commonly used qualifiers

Code/Syntax Description

* Repeat zero times or more times
+   Repeat one or more times
? Repeat zero or once
{n} Repeat n times
{n,} Repeat n times or more
{n,m} Repeat n to m times

3. Commonly used antonyms

Code/Grammar Description

W Matches any character that is not a letter, number, underscore, or Chinese character
S Matches any character that is not a whitespace character
D Matches any character that is not a digit
B Matches something other than the beginning of a word Or the ending position
[^x] Matches any character except x
[^aeiou] Matches any character except the letters aeiou