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[Consolidating the PHP series] PHP regular expressions

高洛峰
高洛峰Original
2016-10-09 11:48:071203browse

【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


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