Mac*_*ski 17
你可能想知道它是如何工作的.我将尝试通过各种方法解释它应该如何完成.我们将首先介绍正则表达式的工作原理及其使用方法.
在计算中,正则表达式(缩写为regex或regexp)是形成搜索模式的字符序列,主要用于与字符串的模式匹配,或字符串匹配,即"查找和替换"类操作.
基本语法
要首先使用正则表达式,您需要学习语法.此语法由一系列字母,数字,点,连字符和特殊符号组成,我们可以使用不同的括号将它们组合在一起.
^ The circumflex symbol matches the beginning of the input string or line, although in some cases it can be omitted
$ Same as with the circumflex symbol, the dollar sign matches the end of the input string or line
. The period matches any single character
? It will match the preceding pattern zero or one times
+ It will match the preceding pattern one or more times
* It will match the preceding pattern zero or more times
| Boolean OR
- Used when describing a range of elements
() Groups pattern elements together
[] Matches any single character between the square brackets
{min, max} Used to match exact character counts, where min and max are integers
\d Matches any single digit
\D Matches any single non digit caharcter
\w Matches any alpha numeric character including underscore (_)
\W Matches any non alpha numeric character excluding the underscore character
\s Matches any single whitespace character
括号
[]在正则表达式的上下文中使用时,括号具有特殊含义.它们用于查找一系列字符.
[0-9] Matches any decimal digit from 0 through 9.
[a-z] Matches any character from lowercase a through lowercase z.
[A-Z] Matches any character from uppercase A through uppercase Z.
[a-Z] Matches any character from lowercase a through uppercase Z.
例子
让我们来看看如何正确使用运算符.我们将用这个词的例子来做这件事hello.
/hello/ Matches the word hello
/^hello/ Matches hello at the start of a string. Possible matches are hello or helloworld, but not worldhello
/hello$/ Matches hello at the end of a string or line.
/he.o/ Matches any character between he and o. Possible matches are helo or heyo, but not hello
/he?llo/ Matches either hllo or hello
/hello+/ Matches hello one or more times. E.g. matches hello or hellohello
/he*llo/ Matches llo, hello or hehello, but not hellooo
/hello|world/ Matches either hello or world
/(A-Z)/ Using the hyphen character to denote a range, matches every uppercase character from A to Z. E.g. A, B, C…
/[abc]/ Matches any single character a, b or c
/abc{1}/ Matches precisely one c character after the characters ab. E.g. matches abc, but not abcc
/abc{1,}/ Matches one or more c character after the characters ab. E.g. matches abc or abcc
/abc{2,4}/ Matches between two and four c character after the characters ab. E.g. matches abcc, abccc or abcccc, but not abc
最普遍的
[^a-zA-Z] Matches any string not containing any of the characters ranging from a through z and A through Z.
p.p Matches any string containing p, followed by any character, in turn followed by another p.
^.{2}$ Matches any string containing exactly two characters.
<b>(.*)</b> Matches any string enclosed within <b> and </b>.
p(hp)* Matches any string containing a p followed by zero or more instances of the sequence hp.
首先让我们看看如何构建URL.我们只有几个选择:
http://example.com/https://example.com/ftp://example.com/www.example.comuser@example.com127.0.0.1http://example.com:8080/http://,https://,ftp,www,mail,ip和port.
方法1(1/10分)
// Only mails
$match = preg_match('/[^\x00-\x20()<>@,;:\\".[\]\x7f-\xff]+(?:\.[^\x00-\x20()<>@,;:\\".[\]\x7f-\xff]+)*\@[^\x00-\x20()<>@,;:\\".[\]\x7f-\xff]+(?:\.[^\x00-\x20()<>@,;:\\".[\]\x7f-\xff]+)+/', $string, $array);
方法2(5/10分)
// Without ports, www-s, ip-s and mails
$text = ereg_replace("[[:alpha:]]+://[^<>[:space:]]+[[:alnum:]/]","<a href=\"\\0\">\\0</a>", $text);
方法3(10/10分)
/* Proposed by:
* Søren Løvborg
* http://stackoverflow.com/users/136796/soren-lovborg
*/
$rexProtocol = '(https?://)?';
$rexDomain = '((?:[-a-zA-Z0-9]{1,63}\.)+[-a-zA-Z0-9]{2,63}|(?:[0-9]{1,3}\.){3}[0-9]{1,3})';
$rexPort = '(:[0-9]{1,5})?';
$rexPath = '(/[!$-/0-9:;=@_\':;!a-zA-Z\x7f-\xff]*?)?';
$rexQuery = '(\?[!$-/0-9:;=@_\':;!a-zA-Z\x7f-\xff]+?)?';
$rexFragment = '(#[!$-/0-9:;=@_\':;!a-zA-Z\x7f-\xff]+?)?';
function callback($match)
{
// Prepend http:// if no protocol specified
$completeUrl = $match[1] ? $match[0] : "http://{$match[0]}";
return '<a href="' . $completeUrl . '">'
. $match[2] . $match[3] . $match[4] . '</a>';
}
$text = preg_replace_callback("&\\b$rexProtocol$rexDomain$rexPort$rexPath$rexQuery$rexFragment(?=[?.!,;:\"]?(\s|$))&",
'callback', htmlspecialchars($text));
你可以在我的答案中写下自己的想法.
我在写信...