Regular expression processing function_PHP tutorial
前面我们已经学习了正则表达式的基础语法,包括了定界符、原子、元字符和模式修正 符。实际上正则表达式想要起作用的话,就必须借用正则表达式处理函数。本节我们就来介绍一下PHP中基于perl的正则表达式处理函数,主要包含了分割, 匹配,查找,替换等等处理操作,依旧是配合示例讲解,让我们开始吧。
和正则表达式一样,正则表达式处理函数不能够独立使用,而这必须相结合,才能够完成特定的功能。在前面我们也说过,基于perl的正则表达式要快于POXIS正则表达式处理函数,所以我们只介绍以preg开头的基于perl的正则表达式。注意:在能偶使用字符串函数处理的时候,就不要使用正则表达式来处理字符串,因为字符串处理函数更快。
下面我们来看一些常用的正则表达式处理函数。
1,preg_match()函数。
函数preg_match()执行一个正则表达式匹配,其定义如下:
<ol class="dp-c"><li class="alt"><span><span>int preg_match ( string </span><span class="vars">$pattern</span><span> , string </span><span class="vars">$subject</span><span> [, </span><span class="keyword">array</span><span> &</span><span class="vars">$matches</span><span> [, int </span><span class="vars">$flags</span><span> = 0 [, int </span><span class="vars">$offset</span><span> = 0 ]]] ) </span></span></li></ol>
实际上就是搜索subject中匹配pattern的部分, 以保存在数组matches中.请看示例:
<ol class="dp-c"> <li class="alt"><span><span><?php </span></span></span></li> <li><span> </span></li> <li class="alt"> <span> </span><span class="vars">$pattern</span><span> = </span><span class="string">'/<b>.*?</b>/'</span><span>; </span> </li> <li> <span> </span><span class="vars">$string</span><span> = </span><span class="string">'<b>welcome</b> <b>to</b> <b>phpfuns</b>dsadsadas'</span><span>; </span> </li> <li class="alt"> <span> </span><span class="keyword">if</span><span> (preg_match(</span><span class="vars">$pattern</span><span>, </span><span class="vars">$string</span><span>, </span><span class="vars">$arr</span><span>)) { </span> </li> <li> <span> </span><span class="func">echo</span><span> </span><span class="string">"正则表达式<b>{$pattern}</b>和字符串<b>{$string}</b>匹配成功<br>"</span><span>; </span> </li> <li class="alt"> <span> print_r(</span><span class="vars">$arr</span><span>); </span> </li> <li> <span> } </span><span class="keyword">else</span><span> { </span> </li> <li class="alt"> <span> </span><span class="func">echo</span><span> </span><span class="string">"<font>正则表达式{$pattern}和字符串{$string}匹配失败</font>"</span><span>; </span> </li> <li><span> } </span></li> <li class="alt"><span> ?> </span></li> <li><span> </span></li> </ol>2,preg_match_all()函数。
函数preg_match_all()函数执行一个全局正则表达式匹配,其定义和preg_match()函数一致,只不过匹配了全部结果。请看示例:
<ol class="dp-c"> <li class="alt"><span><span><?php </span></span></span></li> <li> <span> </span><span class="vars">$pattern</span><span> = </span><span class="string">'/<b>.*?</b>/'</span><span>; </span> </li> <li class="alt"> <span> </span><span class="vars">$string</span><span> = </span><span class="string">'<b>welcome</b> <b>to</b> <b>phpfuns</b>dsadsadas'</span><span>; </span> </li> <li> <span> </span><span class="keyword">if</span><span> (preg_match_all(</span><span class="vars">$pattern</span><span>, </span><span class="vars">$string</span><span>, </span><span class="vars">$arr</span><span>)) { </span> </li> <li class="alt"> <span> </span><span class="func">echo</span><span> </span><span class="string">"正则表达式<b>{$pattern}</b>和字符串<b>{$string}</b>匹配成功<br>"</span><span>; </span> </li> <li> <span> print_r(</span><span class="vars">$arr</span><span>); </span> </li> <li class="alt"> <span> } </span><span class="keyword">else</span><span> { </span> </li> <li> <span> </span><span class="func">echo</span><span> </span><span class="string">"<font>正则表达式{$pattern}和字符串{$string}匹配失败</font>"</span><span>; </span> </li> <li class="alt"><span> } </span></li> <li><span> ?> </span></li> <li class="alt"><span> </span></li> </ol>
依旧是上面的示例(只换了正则处理函数为preg_match_all()),但是匹配的结果数组内容不一样了。
3, preg_replace()函数
函数preg_replace()执行一个正则表达式替换,其定义如下:
mixed preg_replace ( mixed $pattern , mixed $replacement , mixed $subject [, int $limit = -1 [, int &$count ]] )
实际上就是搜索subject中匹配pattern的部分, 以replacement进行替换.其中limit指的是每个模式在每个subject上进行替换的最大次数. 默认是 -1(无限). 如果指定count,将会被填充为完成的替换次数.
注意:
A,如果subject是一个数组, preg_replace()返回一个数组, 其他情况下返回一个字符串.
B,如果匹配被查找到, 替换后的subject被返回, 其他情况下返回没有改变的subject. 如果发生错误, 返回NULL .
C,子模式可以应用到参数replacement中,使用方式为n或者${n}。(在正则表达式的模式中我们只能使用n的形式来获取已经匹配的子模式,切记!)
D,如果使用模式修正符e,则参数replacement中可以解析函数。(在其它的正则表达式处理函数中,模式修正符e均被忽略!)
请看下面的综合示例:
<ol class="dp-c"> <li class="alt"><span><span><?php </span></span></span></li> <li> <span> </span><span class="vars">$pattern</span><span> = </span><span class="string">'/(php)|(mysql)/e'</span><span>; </span> </li> <li class="alt"> <span> </span><span class="vars">$string</span><span> = </span><span class="string">'这个字符串中的php和mysql被替换成大写的了!'</span><span>; </span> </li> <li> <span> </span><span class="vars">$result</span><span> = preg_replace(</span><span class="vars">$pattern</span><span>, </span><span class="string">'strtoupper("${1}2")'</span><span>, </span><span class="vars">$string</span><span>, -1, </span><span class="vars">$count</span><span>); </span> </li> <li class="alt"> <span> </span><span class="func">echo</span><span> </span><span class="vars">$result</span><span>.</span><span class="string">'<br>'</span><span>; </span> </li> <li> <span> </span><span class="func">echo</span><span> </span><span class="vars">$count</span><span>; </span> </li> <li class="alt"><span>?> </span></li> </ol>
上例中,我们使用了模式修正符e,这样的话strtoupper()函数就可以当作字符串被解析,这就是模式修正符e的作用!而参数${1}和2分别是子模式1和子模式2。上例的作用就是将字符串$string中匹配到的子模式php和mysql替换成大写字母!
4,preg_split()函数。
preg_split执行一个正则表达式分隔字符串。其定义如下:
array preg_split ( string $pattern , string $subject [, int $limit = -1 [, int $flags = 0 ]] )
实际上就是将subject按照pattern分割,返回分割后的数组。其中,limit将限制分隔得到的子串最多只有limit个, 返回的最后一个子串将包含所有剩余部分.limit值为-1, 0或null时都代表"不限制"。
我们来看一个示例:
<ol class="dp-c"> <li class="alt"><span><span><?php </span></span></span></li> <li> <span> </span><span class="vars">$pattern</span><span> = </span><span class="string">'/<p>(.*?)</p>/'</span><span>; </span> </li> <li class="alt"> <span> </span><span class="vars">$string</span><span> = </span><span class="string">'这个字符串中的<p>php</p>和<p>mysql</p>被分割了!'</span><span>; </span> </li> <li> <span> </span><span class="vars">$result</span><span> = preg_split(</span><span class="vars">$pattern</span><span>, </span><span class="vars">$string</span><span>, -1, PREG_SPLIT_DELIM_CAPTURE); </span> </li> <li class="alt"> <span> print_r(</span><span class="vars">$result</span><span>); </span> </li> <li><span> ?> </span></li> <li class="alt"><span> </span></li> </ol>
上例中,我们使用了常量PREG_SPLIT_DELIM_CAPTURE设 置返回结果中包含子模式(如果设置为PREG_SPLIT_NO_EMPTY,preg_split()将进返回分隔后的非空部分。)我们如果把上例中正 则表达式的括号去掉,则结果中不再包含php和mysql这两个匹配成功的子模式。
常用的正则表达式处理函数我们就介绍完了,本节的例子可能会难一些,但希望大家还是认真的试验并体会一下,后面的正则表达式应用部分,我们会经常使用正则表达式处理函数。
原文地址:

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

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

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),

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

SublimeText3 Chinese version
Chinese version, very easy to use