Summary of practical regular expressions in PHP

这篇文章主要介绍了PHP经典实用正则表达式,结合具体实例总结分析了php基于正则实现验证、查找、匹配等相关操作技巧,需要的朋友可以参考下

对于开发人员来说，正则表达式是一个非常有用的功能，它提供了 查找，匹配，替换 句子，单词，或者其他格式的字符串。这里介绍了几个超实用的php正则表达式，需要的朋友可以参考下。

1. 验证域名检验一个字符串是否是个有效域名

<?php
$url = "https://www.baidu.com";
if (preg_match(&#39;/^(http|https|ftp):\/\/([A-Z0-9][A-Z0-9_-]*(?:.[A-Z0-9][A-Z0-9_-]*)+):?(d+)?\/?/i&#39;, $url)) {
 echo "Your url is ok.";
} else {
 echo "Wrong url.";
}

2. 从一个字符串中 突出某个单词

这是一个非常有用的在一个字符串中匹配出某个单词 并且突出它，非常有效的搜索结果

<?php
$text = "Sample sentence from KomunitasWeb, regex has become popular in web programming. Now we learn regex. According to wikipedia, Regular expressions (abbreviated as regex or
regexp, with plural forms regexes, regexps, or regexen) are written in a formal language that can be interpreted by a regular expression processor";
$text = preg_replace("/(regex)/i", &#39;<span style="background:#5fc9f6">1</span>&#39;, $text);
echo $text;

function get_the_title(){
  return 'Save the search.php file and open style.css. Append the following line to it: ';
}
$s = 'and php';
$title  = get_the_title();
$keys= explode(" ",$s);
$title  = preg_replace('/('.implode('|', $keys) .')/iu',
&#39;<strong>\0</strong>&#39;,
$title);
echo $title;

3. 从HTML文档中获得全部图片

如果你曾经希望去获得某个网页上的全部图片，这段代码就是你需要的，你可以轻松的建立一个图片下载机器人

<?php
$images = array();
$data = file_get_contents(&#39;https://www.baidu.com&#39;);
preg_match_all(&#39;/(img|src)=("|\&#39;)[^"\&#39;>]+/i&#39;, $data, $media);
unset($data);
$data=preg_replace(&#39;/(img|src)("|\&#39;|="|=\&#39;)(.*)/i&#39;,"$3",$media[0]);
foreach($data as $url)
{
 $info = pathinfo($url);
 if (isset($info[&#39;extension&#39;]))
 {
  if (($info[&#39;extension&#39;] == &#39;jpg&#39;) ||
  ($info[&#39;extension&#39;] == &#39;jpeg&#39;) ||
  ($info[&#39;extension&#39;] == &#39;gif&#39;) ||
  ($info[&#39;extension&#39;] == &#39;png&#39;))
  array_push($images, $url);
 }
}
var_dump($images);

4. 匹配一个XML或者HTML标签

这个简单的函数有两个参数：第一个是你要匹配的标签，第二个是包含XML或HTML的变量，再强调下，这个真的很强大

<?php
function get_tag( $tag, $xml ) {
  $tag = preg_quote($tag);
  output($tag);
  preg_match_all(&#39;/<&#39;.$tag.&#39;[^>]*>(.*?)<\/&#39;.$tag.&#39;>./&#39;,
    $xml,
    $matches,
    PREG_PATTERN_ORDER
  );
  return $matches[1];
}
$xml = &#39;<span>bb<a>bbb</a><a>ccc</a></span><span>bb<a>aa</a><p><a>ddd</a></p></span>&#39;;
$tag = &#39;a&#39;;
$return = get_tag($tag, $xml);
var_dump($return);
/*
array(2) {
 [0]=>
 array(3) {
  [0]=>
  string(11) "bbb<"
  [1]=>
  string(10) "aa<"
  [2]=>
  string(11) "ddd<"
 }
 [1]=>
 array(3) {
  [0]=>
  string(3) "bbb"
  [1]=>
  string(2) "aa"
  [2]=>
  string(3) "ddd"
 }
}
array(3) {
 [0]=>
 string(3) "bbb"
 [1]=>
 string(2) "aa"
 [2]=>
 string(3) "ddd"
}
*/

以上就是本文的全部内容，希望对大家的学习有所帮助。

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