Home Backend Development PHP Tutorial Chapter 9 Regular Expressions_PHP Tutorial

Chapter 9 Regular Expressions_PHP Tutorial

Jul 13, 2016 am 10:34 AM
aspnet software programming

注:文章出自李炎恢PHP视频教程,本文仅限交流使用,不得用于商业用途,否则后果自负。

学习要点:
1.正则表达式语法(Perl 风格)
2.正则表达式中的元素
3.Perl 风格函数

 

处理字符串时,有很多较为复杂的字符串用普通的字符串处理函数无法干净的完成。比
如说,可能需要验证一个Email 地址是否合法,为此需要查看许多不容易检查的规则。这正
是正则表达式的用武之地。正则表达式是功能强大而简明的字符组,其中可以包含大量的逻
辑,特别值得一提的是正则表达式相当简短。

一.正则表达式语法(Perl风格)

Perl 一直被认为是最伟大的解析语言之一,它提供了一种全面的正则表达式,即使是最
复杂的字符串模式,也可以用这种正则表达式语言搜索和替换。PHP 开发人员认识到,与
其重新发明正则表达式,不如让PHP 用户直接使用声名赫赫的Perl 正则表达式语言,即Perl
风格的函数。
模式规则:/php/ 在字符串前后加上两条斜杠即可。
匹配函数:preg_match()函数在字符串中搜索模式,如果存在则返回true,否则返回false。

<?<span php
</span><span preg_match</span>('/php/','php'<span );
</span>?>
Copy after login

二.正则表达式中的元素

正则表达式中包含三种元素分别为:量词、元字符、修饰符

量词

元字符

修饰符

三.Perl风格函数

PHP 为使用Perl 兼容的正则表达式搜索字符串提供了7 个函数,包括:preg_grep()、
preg_match()、preg_match_all()、preg_auote()、preg_replace()、preg_replace_callback()和
preg_split()。
搜索字符串:preg_grep()函数搜索数组中的所有元素,返回由与某个模式匹配的所有元
素组成的数组。

<?<span php
</span><span $language</span> = <span array</span>('php','asp','jsp','python','ruby'<span );
</span><span print_r</span>(<span preg_grep</span>('/p$/',<span $language</span><span ));
</span>?>
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搜索模式:preg_match()函数在字符串中搜索模式,如果存在则返回true,否则返回false。

<?<span php
</span><span echo</span> <span preg_match</span>('/php[1-6]/','php5'<span );
</span>?>
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电子邮件验证小案例(分组应用)

<?<span php
</span><span $mode</span> = '/([\w\.\_]{2,10})@(\w{1,}).([a-z]{2,4})/'<span ;
</span><span $string</span> = 'yc60.com@gmail.com'<span ;
</span><span echo</span> <span preg_match</span>(<span $mode</span>,<span $string</span><span );
</span>?>
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匹配模式的所有出现:preg_match_all()函数在字符串中匹配模式的所有出现,然后将所
有匹配到的全部放入数组。

<?<span php
</span><span preg_match_all</span>('/php[1-6]/','php5sdfphp4sdflljkphp3sdlfjphp2',<span $out</span><span );
</span><span print_r</span>(<span $out</span><span );
</span>?>
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定界特殊的正则表达式:preg_quote()在每个对于正则表达式语法而言有特殊含义的字
符前插入一个反斜线。这些特殊字符包含:$ ^ * () + = {} [] | \\ : <>。

<?<span php
</span><span echo</span> <span preg_quote</span>('PHP的价格是:$150'<span );
</span>?>
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替换模式的所有出现:preg_replace()函数搜索到所有匹配,然后替换成想要的字符串返
回出来。

<?<span php
</span><span echo</span> <span preg_replace</span>('/php[1-6]/','python','This is a php5,This is a php4'<span );
</span>?>
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ubb 小案例:贪婪问题+分组使用()

<?<span php
</span><span $mode</span> = '/\[b\](.*)\[\/b\]/U'<span ;
</span><span $replace</span> = '<strong>\1</strong>'<span ;
</span><span $string</span> = 'This is a [b]php5[/b],This is a [b]php4[/b]'<span ;
</span><span echo</span> <span preg_replace</span>(<span $mode</span>,<span $replace</span>,<span $string</span><span );
</span>?>
Copy after login

以不区分大小写的方式将字符串划分为不同的元素:preg_split()用来分割不同的元素。

<?<span php
</span><span print_r</span>(<span preg_split</span>('/[\.@]/','yc60.com@gmail.com'<span  ));
</span>?>
Copy after login

注:目前为PHP 使用POSIX 风格的正则表达式搜索字符串提供了7 个函数,包括:ereg()、
ereg_replace()、eregi()、eregi_replace()、split()、spliti()和sql_regcase()。
PS:和Perl 风格基本相同,可以参考手册自行学习。

www.bkjia.comtruehttp://www.bkjia.com/PHPjc/748763.htmlTechArticle注:文章出自李炎恢PHP视频教程,本文仅限交流使用,不得用于商业用途,否则后果自负。 学习要点: 1.正则表达式语法(Perl 风格) 2.正...
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