[Consolidating PHP Basics 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 escapesome special symbols, such as ".", "/"

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

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

　　　- Parentheses are used to specify subexpression (also called grouping), and then you can specify the number of repetitions of this subexpression, ([-+.]w+ )*

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

　　　-                        Matches any character except line breaks

　　4) Code example

　

<?<span style="color: #000000;">php
  </span><span style="color: #800080;">$email</span> = 'sishuinianhua369@126.com'<span style="color: #000000;">;
  </span><span style="color: #800080;">$preg</span> = '/\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*/'<span style="color: #000000;">;
  </span><span style="color: #800080;">$res</span> = <span style="color: #008080;">preg_match</span>(<span style="color: #800080;">$preg</span>, <span style="color: #800080;">$email</span>, <span style="color: #800080;">$preg_res</span><span style="color: #000000;">);
  </span><span style="color: #008080;">var_dump</span>(111,<span style="color: #800080;">$res</span>,<span style="color: #800080;">$preg_res</span>);<span style="color: #0000ff;">exit</span>;

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

2. URL expression:

　1) [a-zA-z]+://[^s]+

　2) Analysis:

　　-- ^

 放 & gt; put it before the expression, indicating that the current character starts. (/^n/i, means starting with n). 　　-- s matches any whitespace character

3. Appendix

1. Commonly used metacharactersCode Description. Matches any character except line breaks

w Matches letters or numbers or underscores

s Matches any whitespace characterd Matches numbersb Matches the beginning or end of a word
^ Matches the beginning of the string
$ Matches the end of the string





2. Commonly used qualifiers

Code/Syntax Description

* Repeat zero 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 non-digit characterB 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