How PHP matches the data outside the IMG tag and replaces it with the IMG data unchanged

When I add an article, I need to automatically generate anchor text, keyword to match the content of the article, will match to the IMG alt and title value, the picture will appear abnormal.
Dear God, help me solve it! Thanks, man.

The original wanted is

这些文字加链接

Error content:

My code is written like this:

/** * 多关键词替换，每个替换一次 * @param  Mixed $search   查找目标值 * @param  Mixed $replace  替换值 * @param  Mixed $subject  执行替换的字符串／数组 * @param  Int   $limit    允许替换的次数，默认为-1，不限次数 * @return Mixed */function str_replace_limit($search, $replace, $subject, $limit=-1){    if(is_array($search)){        foreach($search as $k=>$v){            $search[$k] = '`'. preg_quote($search[$k], '`'). '`';        }    }else{        $search = '`'. preg_quote($search, '`'). '`';    }    return preg_replace($search, $replace, $subject, $limit);}foreach ($keylink as $k){        $keyArray[] = $k->word;        $url = 'url.'" style="color:red;font-size:1.2em;">'.$k->word.'';        $replacement[] = $url;}

Reply content:

When I add an article, I need to automatically generate anchor text, keyword to match the content of the article, will match to the IMG alt and title value, the picture will appear abnormal.
Dear God, help me solve it! Thanks, man.

The original wanted is

这些文字加链接

Error content:

My code is written like this:

/** * 多关键词替换，每个替换一次 * @param  Mixed $search   查找目标值 * @param  Mixed $replace  替换值 * @param  Mixed $subject  执行替换的字符串／数组 * @param  Int   $limit    允许替换的次数，默认为-1，不限次数 * @return Mixed */function str_replace_limit($search, $replace, $subject, $limit=-1){    if(is_array($search)){        foreach($search as $k=>$v){            $search[$k] = '`'. preg_quote($search[$k], '`'). '`';        }    }else{        $search = '`'. preg_quote($search, '`'). '`';    }    return preg_replace($search, $replace, $subject, $limit);}foreach ($keylink as $k){        $keyArray[] = $k->word;        $url = 'url.'" style="color:red;font-size:1.2em;">'.$k->word.'';        $replacement[] = $url;}

Can look at the code is not

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