Simple database operation Model class implemented in PHP

The example in this article describes the simple database operation Model class implemented in PHP. Share it with everyone for your reference, the details are as follows:

This database model class can realize the addition, deletion, modification and query of the database and simplify the database operation.

1. config.php code:

<?php
 define("HOSTNAME","127.0.0.1");
 define("USERNAME","root");
 define("PASSWORD","");
 define("DATANAME","class");

2. Usage code:

<?php
 require("./config.php");
 class Model{
  private $link;
  //构造函数，初始化数据库连接
  public function __construct(){
   $this -> link = mysqli_connect(HOSTNAME,USERNAME,PASSWORD,DATANAME) or die("数据库连接失败");
   mysqli_set_charset($this -> link,"utf8");
  }
  //查找 1.表名 2.条件 3.值 如果不添加条件或者值，就全部查询
  public function find($table="",$key="",$value=""){
   if(!$key||!$value){
    $sql = "select * from {$table}";
   }else{
    $sql = "select * from {$table} where {$key} = &#39;{$value}&#39;";
   }
   $res = mysqli_query($this -> link,$sql);
   $arr = mysqli_fetch_all($res,MYSQLI_ASSOC);
   mysqli_free_result($res);
   return $arr;
  }
  //增加 1.表名 2.需要插入的字段 3.值1
  public function ins($table="",$zd="name,score",$value=""){
   $arr = explode(",",$value);
   $str = "";
   foreach($arr as $k => $v){
    $str .= "&#39;".$v."&#39;".",";
   }
   $str = rtrim($str,",");
   $sql = "insert into {$table}({$zd})values({$str})";
   $res = mysqli_query($this -> link,$sql);
   return mysqli_insert_id($this -> link);
  }
  //修改 1.表名 2.修改字段 3.值 4.条件 5.值
  public function upd($table="",$key="",$value="",$key2="",$value2=""){
   $sql = "update {$table} set {$key}=&#39;{$value}&#39; where {$key2}=&#39;{$value2}&#39;";
   $res = mysqli_query($this -> link,$sql);
   return mysqli_affected_rows($this -> link);
  }
  //删除 1.表名 2.条件 3.值
  public function del($table="",$key="",$value=""){
   $sql = "delete from {$table} where {$key}=&#39;{$value}&#39;";
   $res = mysqli_query($this -> link,$sql);
   return mysqli_affected_rows($this -> link);
  }
  //析构函数
  public function __destruct(){
   if(isset($res))
    mysqli_free_result($res);
   mysqli_close($this -> link);
  }
 }
 $m = new Model();
 //var_dump($m -> find("stu","id"));
 var_dump($m -> ins("stu","name","zhu"));
 //var_dump($m -> upd("stu","name","dujianing","id","1"));
 //var_dump($m -> del("stu","name","li"));
?>