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>?>
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>?>
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>?>
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>?>
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 $out</span><span ); </span>?>
定界特殊的正则表达式:preg_quote()在每个对于正则表达式语法而言有特殊含义的字
符前插入一个反斜线。这些特殊字符包含:$ ^ * () + = {} [] | \\ : 。
<?<span php </span><span echo</span> <span preg_quote</span>('PHP的价格是:$150'<span ); </span>?>
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>?>
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>?>
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>?>
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。

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Atom editor mac version download
The most popular open source editor

SublimeText3 Linux new version
SublimeText3 Linux latest version

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

Zend Studio 13.0.1
Powerful PHP integrated development environment

SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.