php实现的简单数据库操作Model类

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

<?php /*  作者：shyhero  */ 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 {$key} = '{$value}'";   }   $res = mysqli_query($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){    $str .= "'".$v."'".",";   }   $str = rtrim($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 {$key}='{$value}' where {$key2}='{$value2}'";   $res = mysqli_query($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 {$key}='{$value}'";   $res = mysqli_query($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"));?>