What is the usage of model in php

Usage of model in php: 1. Create a PHP sample file; 2. Introduce the configuration file; 3. Create the Model class; 4. Initialize the database connection operation; 5. Execute and send SQL statements; 6. Pass "new Model("table name");" can be debugged.

The operating environment of this article: Windows 7 system, PHP version 7.4, DELL G3 computer

What is the usage of model in php?

PHP model Model class encapsulates database operation examples

PHP model Model class encapsulates database operations, and combines the example form to analyze the database operations encapsulated by PHP using mysqli Related implementation and usage skills:

The details are as follows:

<?php
  //引入配置文件
  include "./config.php";
  class Model
  {
    public $link;//存储连接对象
    public $tableName = "";//存储表名
    public $field = "*";//存储字段
    public $allFields = [];//存储当前表所有字段
    public $where = "";//存储where条件
    public $order = "";//存储order条件
    public $limit = "";//存储limit条件
    /**
     * 构造方法 初始化
     * @param string $tableName 要操作的表名
     */
    public function __construct($tableName)
    {
      //1.存储操作的表名
      $this->tableName = PRE.$tableName;
      //2.初始化连接数据库
      $this->getConnect();
      //3.获得当前表的所有字段
      $this->getFields();
    }
    /**
     * 初始化连接数据库操作
     */
    public function getConnect()
    {
      //1.连接数据库
      $this->link = mysqli_connect(HOST,USER,PWD,DB,PORT);
      //2.判断连接
      if (mysqli_connect_errno($this->link)>0){
        echo mysqli_connect_error($this->link);
        exit;
      }
    }
    /**
     * 执行并发送SQL(查询)
     * @param string $sql 要查询的SQL语句
     * @return array 返回查询出来的二维数组
     */
    public function query($sql)
    {
      $result = mysqli_query($this->link,$sql);
      if ($result && mysqli_num_rows($result)>0) {
       $arr = [];
       while($row = mysqli_fetch_assoc($result)){
          $arr[] = $row;
       }
      }
    return $arr;
    }
    /**
     * 获取当前表的所有字段
     */
    public function getFields()
    {
      //查看表结构
      $sql = "desc {$this->tableName}";
      //执行并发送SQL
      $result = $this->query($sql);
      $fields = [];
      foreach ($result as $k => $v){
        $fields[] = $v[&#39;Field&#39;];
      }
      $this->allFields = $fields;
    }
    /**
     * 执行并发送SQL语句(增删改)
     * @param string $sql 要执行的SQL语句
     * @return bool|int|string 添加成功则返回上一次操作id,删除修改操作则返回true,失败则返回false
     */
    public function exec($sql)
    {
      $result = mysqli_query($this->link,$sql);
      //处理结果集
      if ($result && mysqli_affected_rows($this->link)>0){
        //判断是否为添加操作，是则返回上一次执行的id
        if (mysqli_insert_id($this->link)){
          return mysqli_insert_id($this->link);
        }
        //删除修改操作成功则返回true
        return true;
      }else{
        //未执行成功则返回false
        return false;
      }
    }
    /**
     * 查询多条数据
     */
    public function select()
    {
      $sql = "select {$this->field} from {$this->tableName} {$this->where} {$this->order} {$this->limit}";
      //执行并发送SQL
      return $this->query($sql);
    }
    /**
     * 查询一条数据
     * @param string $id 要查询的id
     * @return array 返回一条数据
     */
    public function find($id="")
    {
      //判断id是否存在
      if (empty($id)){
        $where = $this->where;
      }else{
        $where = "where id={$id}";
      }
      $sql = "select {$this->field} from {$this->tableName} {$where} limit 1";
      //执行并发送sql
      $result = $this->query($sql);
      //返回一条数据
      return $result[0];
    }
    /**
     * 设置要查询的字段信息
     * @param string $field 要查询的字段
     * @return object 返回自己，保证连贯操作
     */
    public function field($field)
    {
      //判断字段是否存在
      if (empty($field)){
        return $this;
      }
      $this->field = $field;
      return $this;
    }
    /**
     * 统计总条数
     * @return int 返回总数
     */
    public function count()
    {
      //准备SQL语句
      $sql = "select count(*) as total from {$this->tableName} limit 1";
      $result = $this->query($sql);
      //返回总数
      return $result[0][&#39;total&#39;];
    }
    /**
     * 添加操作
     * @param array $data 要添加的数组
     * @return bool|int|string 添加成功则返回上一次操作的id,失败则返回false
     */
    public function add($data){
      //判断是否是数组
      if (!is_array($data)){
        return $this;
      }
      //判断是否全是非法字段
      if (empty($data)){
        die("非法数据");
      }
      //过滤非法字段
      foreach ($data as $k => $v){
        if (!in_array($k,$this->allFields)){
          unset($data[$k]);
        }
      }
      //将数组中的键取出
      $keys = array_keys($data);
      //将数组中取出的键转为字符串拼接
      $key = implode(",",$keys);
      //将数组中的值转化为字符串拼接
      $value = implode("&#39;,&#39;",$data);
      //准备SQL语句
      $sql = "insert into {$this->tableName} ({$key}) values(&#39;{$value}&#39;)";
      //执行并发送SQL
      return $this->exec($sql);
    }
    /**
     * 删除操作
     * @param string $id 要删除的id
     * @return bool 删除成功则返回true,失败则返回false
     */
    public function delete($id="")
    {
      //判断id是否存在
      if (empty($id)){
        $where = $this->where;
      }else{
        $where = "where id={$id}";
      }
      $sql = "delete from {$this->tableName} {$where}";
      echo $sql;
      //执行并发送
      return $this->exec($sql);
    }
    /**
     * 修改操作
     * @param array $data 要修改的数组
     * @return bool 修改成功返回true，失败返回false
     */
    public function update($data){
      //判断是否是数组
      if (!is_array($data)){
        return $this;
      }
      //判断是否是全是非法字段
      if(empty($data)){
        die("非法数据");
      }
      $str = "";
      //过滤非法字段
      foreach ($data as $k => $v){
        if ($k == "id"){
          $where = "where id={$v}";
          unset($data[$k]);
        }
        if (in_array($k,$this->allFields)){
          $str .= "{$k}=&#39;{$v}&#39;,";
        }else{
          unset($data[$k]);
        }
      }
      //判断是否有条件
      if (empty($this->where)){
        die("请输入条件");
      }
      //去掉最右侧的逗号
      $str = rtrim($str,",");
      $sql = "update {$this->tableName} set {$str} {$this->where}";
      return $this->exec($sql);
    }
    /**
     * where条件
     * @param string $where 输入的where条件
     * @return $this 返回自己，保证连贯操作
     */
    public function where($where)
    {
      $this->where = "where ".$where;
      return $this;
    }
    /**
     * order排序条件
     * @param string $order 以此为基准进行排序
     * @return $this 返回自己，保证连贯操作
     */
    public function order($order)
    {
      $this->order = "order by ".$order;
      return $this;
    }
    /**
     * limit条件
     * @param string $limit 输入的limit条件
     * @return $this 返回自己，保证连贯操作
     */
    public function limit($limit)
    {
      $this->limit = "limit ".$limit;
      return $this;
    }
    /**
     * 析构方法
     * 关闭数据库连接
     */
    public function __destruct()
    {
      mysqli_close($this->link);
    }
  }
 //自行调试
 $a = new Model("表名");
 // var_dump($a->find(3));
 // var_dump($a->select());
  // var_dump($a->count());
  // $res = $a->select();
  //var_dump($res);
?>

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