Detailed explanation of how to filter and replace sensitive words in PHP

With the popularization of the Internet, a large amount of information is spread on the Internet, which also contains bad information, such as violence, pornography, abuse, etc. This information will not only affect the mental health of netizens, but also cause negative social effects. Therefore, during the development process of the website, sensitive words need to be filtered to protect the legitimate rights and interests of netizens. In development, the PHP programming language is a commonly used programming language. This article will introduce in detail how PHP filters and replaces sensitive words.

1. Overview

Normally, we need to determine whether sensitive words appear when accessing comments or publishing content on the website. If they appear, they need to be filtered or replaced. The traditional method is to match through regular expressions, but for longer and more complex words, matching will take a long time, causing the program to run slowly.

Now, we can use the trie tree algorithm in PHP to quickly identify sensitive words and process them.

2. Implementation of trie tree algorithm

The trie tree algorithm, also known as "dictionary tree", is a tree data structure used for fast retrieval. The biggest advantage of using the trie tree algorithm to search is that according to the given number of words, the search time has nothing to do with the length, only the number of words. That is, no matter how long the search string is, the search time is the same. This provides the possibility for PHP to quickly filter sensitive words.

To use the trie tree algorithm to quickly detect and filter sensitive words, we can first create a trie tree to record all sensitive words. For each string that needs to be detected, we can split the string into individual characters and then match them on the trie tree in order. If a position match fails, false is returned. Otherwise, continue the matching of the next character. If the leaf node is finally reached, the match is considered successful and filtering or replacement is performed.

3. Filtering and Replacement Implementation

After filtering sensitive words, you need to perform a replacement operation to replace the sensitive words with "*" or other characters to achieve the effect of protecting the privacy of netizens.

The method for PHP to filter sensitive words and replace them is as follows:

function filterWords($str, $trie,$replaceStr="*"){
    $len = mb_strlen($str);
    $i = 0;
    $result = '';
    while($i<$len){
        $node =$trie;
        $j = $i;
        while($node!=null && $j<$len){
            $t = mb_substr($str, $j, 1);
            $node = $node->$t;
            $j++;
            if($node!=null && $node->end>0){//匹配到最后一个字符
                for($k=$i;$k<$j;$k++){
                    $result.= $replaceStr;
                }
                $i=$j;
                break;
            }
        }
        if($node==null){
            $result.= mb_substr($str, $i, 1);
            $i++;
        }
    }
    return $result;
}

class TrieTree{
    public $next, $end;$v;
    function __construct(){
        $this->next = array();
        $this->end = 0;
        $this->v   = '';
    }
}

function insertTrie(&$trie,$str){
    $len=strlen($str);
    $tmp=$trie;
    for($i=0;$i<$len;$i++){
        $t=$str[$i];
        if(!isset($tmp->next[$t])){
            $tmp->next[$t] = new TrieTree();
        }
        $tmp = $tmp->next[$t];
    }
    $tmp->end=1;
}

$trie = new TrieTree();
$words=array("敏感词1","敏感词2","敏感词3");
foreach ($words as $word) {
    insertTrie($trie,$word);
}
$str="这是一个含有敏感词汇的字符串";
echo filterWords($str,$trie);

The above code is a simple example, using the trie tree algorithm implemented in PHP. Among them, the insertTrie() function is used to insert sensitive words into the trie tree, and the filterWords() function is used to filter sensitive words and perform replacement operations.

4. Summary

As there is a large amount of bad information on the Internet, it is very important to protect the legitimate rights and interests of netizens. Filtering and replacing sensitive words is also one of the effective means to prevent the spread of bad information on the Internet. This article introduces in detail the method of quickly filtering sensitive words in PHP and provides relevant code examples. I hope it will be helpful to PHP developers.

The above is the detailed content of Detailed explanation of how to filter and replace sensitive words in PHP. For more information, please follow other related articles on the PHP Chinese website!