通过一个简单的数据库操作类了解PHP链式操作的实现

class Model{
  public $table; //操作的表;
  private $opt; //查询的参数;
  private $pri; //表的主键;
  private $lastSql; //最后一条sql语句;
  private $error;

  public function __construct($table = ''){
    $this->table = $table;

    $db = @mysql_connect('127.0.0.1' , 'root' , 'admin'); //这里应该通过配置读取进来
    if (!$db)
      exit('抱歉!数据库链接失败!');
    mysql_select_db('tpplh') or exit('对不起,没有这个数据库'); //数据库的选择

    mysql_query("SET NAMES utf8"); //设定数据库字符集;
    $this->getPrimary($table); //获取主键;
    $this->opt(); //初始化查询参数;
  }

  public function getLastSql(){
    return $this->lastSql;
  }

  public function getError(){
    return $this->error();
  }

  #获取表的主键
  private function getPrimary($table){
    $this->lastSql = ' DESC ' . $table;
    $result = $this->query($this->lastSql);
    foreach ($result as $v) {
      if ($v['Key'] == 'PRI') {
        $this->pri = $v['Field'];
        return;
      }
    }
  }

  #初始化查询参数
  private function opt(){
    $this->opt = array('table' => $this->table , 'pri' => $this->pri , 'where' => '' , 'orderby' => '' , 'having' => '' , 'orderway' => '' , 'group' => '' , 'limit' => '' , 'fields' => '*');
  }

  #临时表切换,不用另外在实例化类了;
  public function table($table){
    $this->opt['table'] = $table;
    return $this; //返回切换后的对象;
  }

  public function save($data = null){
    return $this->update($data);
  }

  #update更改
  public function update($data = null){
    if (is_null($data))
      $data = $_POST;
    if (!is_array($data))
      return false;
    if (isset($data[$this->pri])) { //如果里面有主键;就让where条件临时变为主键
      $this->opt['where'] = ' WHERE ' . $this->pri . '=' . $data[$this->pri];
    }
    if (!$this->opt['where']) {
      echo '增删改操作,必须要带where条件!';
      exit;
    }
    $set = ''; //set字符串容器;
    foreach ($data as $n => $v) {
      $set .= $n . "='" . $v . "',";
    }
    $set = rtrim($set , ','); //去掉后面多余的逗号;
    $this->lastSql = "UPDATE " . $this->opt['table'] . ' SET ' . $set . $this->opt['where'];
    return $this->exe($this->lastSql);
  }

  #delete删除:delete from 表名 where 条件;
  public function delete(){
    $where = $this->opt['where'];
    if (!$where) {
      echo 'delete必须设置条件';
      exit;
    }
    $this->lastSql = "DELETE FROM {$this->opt['table']} $where";
    return $this->exe($this->lastSql);
  }

  #insert条件
  public function insert($data = null){
    if (is_null($data))
      $data = $_POST;
    if (!is_array($data))
      return false;
    $field = $value = "";
    $field = implode("," , array_keys($data));
    foreach ($data as $name => $v) {
      $value .= "'" . addslashes($v) . "',";
    }
    $value = substr($value , 0 , -1);
    $this->lastSql = "INSERT INTO " . $this->opt['table'] . "($field) VALUES($value)";
    return $this->exe($this->lastSql);
  }

  public function add($data = null){
    return $this->insert($data);
  }

  #limit 语句:
  public function limit($arg){
    $this->opt['limit'] = " LIMIT $arg";
    return $this;
  }

  #order 语句:
  public function order($arg){
    $this->opt['orderby'] = " ORDER BY $arg";
    return $this;
  }

  #orderway 语句:
  public function orderway($arg){
    $this->opt['orderway'] = " $arg";
    return $this;
  }

  #group 语句:
  public function group($arg){
    $this->opt['group'] = " GROUP BY $arg";
    return $this;
  }

  #where 条件
  public function where($arg){
    $this->opt['where'] = " WHERE $arg";
    return $this;
  }

  #having 语句
  public function having($arg){
    $this->opt['where'] = " HAVING $arg";
    return $this;
  }

  #fields 语句
  public function field($arg){
    $this->opt['fields'] = " $arg";
    return $this;
  }

  #count 语句 统计数量
  public function count(){
    $this->lastSql = "select count(*) as t from " . $this->opt['table'] . $this->opt['where'];
    $count = $this->query($this->lastSql);
    return $count[0]['t'];
  }

  #select 语句
  public function select(){
    $this->lastSql = "SELECT {$this->opt['fields']} FROM {$this->opt['table']}{$this->opt['where']}{$this->opt['orderby']}{$this->opt['orderway']}{$this->opt['group']}{$this->opt['having']}{$this->opt['limit']}";
    //echo $this -> lastSql;die;
    $this->opt(); //查询完执行opt方法重新初始化参数;
    return $this->query($this->lastSql);
  }

  #find 通过主键来查询
  public function find($arg = null){
    if ($this->pri and $arg) {
      $this->opt['where'] = " WHERE {$this->pri}=$arg";
    } else {
      $this->opt['limit'] = " LIMIT 1";
    }
    return $this->select();
  }

  #发送增,删,改sql,成功返回最后一条的id或受影响条数;
  public function exe($sql){
    $this->lastSql = $sql;
    if (mysql_query($sql)) {
      $result = mysql_insert_id() ? mysql_insert_id() : mysql_affected_rows(); //如果该表有一个自增的id,就返回自增的id,如果没有就返回受影响的条数;
      return $result;
    }
  }

  #发送查询的sql语句,返回查询结果数组;
  public function query($sql){
    $this->lastSql = $sql;
    $result = mysql_query($sql);
    if (!$result)
      return $this->error();
    $rows = array(); //用于存储查询的数据;
    while ($row = mysql_fetch_assoc($result)) {
      $rows[] = $row;
    }
    return $rows;
  }

  private function error(){
    return $this->error = mysql_error(); //输出mysql产生的错误信息;
  }
}
?>

总结如下:

1. 链式部分就是对类中属性的进行更改,属性可以是数组
2. 在链式部分最后返回的都是$this
3. 在最后输出方法中获取链式更改掉的属性进行操作