PHP simple database operation class example

/**
*
* @Authot: summer
*
* @E-mail: wenghang1228@me.com
*
* @Data: 2015-02-06
*
* @Project: 数据库操作类Model
*
* @Version:1.0
*
* @版权所有：夏天的风————记录夏天对技术的追求与生活的热爱
*
* @网址: http://www.xtwind.com
**/
class Model{
  public $field;
  public $tabname;
  public $where;
  public $order;
  public $limit;
  //构造函数，链接数据库，给表赋值
  function __construct($tabname){
    mysql_connect(HOST,USER,PASSWORD);
    mysql_select_db(DBNAME);
    mysql_query("set names utf8");
    $this->tabname=$tabname;
  }
  //组合字段
  function field($field){
    $this->$field=$field;
    return $this;
  }
  //组合where条件
  function where($where){
    $this->where="where ".$where;
    return $this;
  }
  //组合order排序条件
  function order($order){
    $this->order="order by ".$order;
    return $this;
  }
  //组合limit限制条数
  function limit($limit){
    $this->limit="limit ".$limit;
    return $this;
  }
  //组合和执行select语句
  function select($all=""){
    if ($all) {
      $sql="select {$all} from {$this->tabname} order by id";
    }else{
      $sql="select {$this->filed} from {$this->tabname} {$this->where} {$this->order} {$this->limit}";
    }
    $rst=mysql_query($sql);
    while ($row=mysql_fetch_assoc($rst)) {
      $rows[]=$row;
    }
    return $rows;
  }
  //组合和执行insert语句
  function insert($post){ //数据库插入操作,接收数组
    foreach ($post as $key => $value) {
      $keys[]=$key;
      $vals[]="'".$valu."'";
    }
    $keyStr=join(",",$keys);
    $valStr=join(",",$vals);
    $sql="insert into {$this->tabname}($keystr) values()";
    if (mysql_query($sql)) {
      return mysql_insert_id();
    }else{
      return false;
    }
  }
  //组合和执行delect语句
  function delect(){
    $sql="delect from {$this->tabname} {$this->where}";
    if (mysql_query($sql)) {
      return mysql_affected_rows();
    }else{
      return false;
    }
  }
  //组合和执行updata语句
  function update($post){
    foreach ($psot as $key => $value) {
      $sets[]="{$key}='{$val}'";
    }
    $setStr=join(",",$sets);
    $sql="update {$this->tabname} set {$setStr} {$this->where} ";
    if (mysql_query($sql)) {
      return mysql_affected_rows();
    }else{
      return false;
    }
  }
  //从表中取一行数据
  function find(){ 
    if ($this->order) {
      $sql="select * from {$this->tabname} {$this->order} limit 1";
    }else{
      $sql="select * from {$this->tabname} order by id limit 1";
    }
    $rst=mysql_query($sql);
    while ($row=mysql_fetch_assoc($rst)) {
      $rows[]=$row;
    }
    return $rows;
  }
  //获取总行数
  function total(){ 
    $sql="select count(*) from {$this->tabname}";
    $rst=mysql_query($sql);
    if ($rst) {
      $row=mysql_fetch_row($rst);
      return $row[0];
    }else{
      return false;
    }
  }
}
//Model类对象工厂
function M($tabname){
  return new Model($tabname);
}
define("HOST","localhost");
define("USER", "root");
define("PASSWORD", "123456");
define("DBNAME", "test")
$user=new Model("user");
$user->field("id,name")->where("id=3")->order("id desc")->limit("3")->select();