What I want to implement is the keyword replacement function. a. img contains keywords and cannot be replaced.
If [Example] is a keyword, the keyword appears in these three situations and cannot be replaced, otherwise it will destroy the html structure

<a href="#" title="这是一个例子而已">这是一个例子而已</a>
<img src="#" alt="我是例子呀">

<a href="#" title="这是一个例子">这是一个例子</a>
<img src="#" alt="我是例子">

<a href="#" title="例子而已">例子而已</a>
<img src="#" alt="例子呀">

被破坏的<img src="#" alt="破坏了<a href="#">例子</a>破坏的可能性有多大？"/>

<?php
    function findword($word,$html){
        $str_reg = '(<a[^>]+>)(.*)('.$word.')(.*)(<\/a[^>]*>)';
        $str_reg .= '|(<img)(.*?)('.$word.')(.*?)(>)' ;
        if(preg_match("/$str_reg/",$html)){
            return true;
        }else{
            return false;
        }
    }
?>

Write a crappy function. It doesn't seem right.