<?php
class Database{
 //只是為了演示，通常情況下數(shù)據(jù)庫的配置是會單獨(dú)寫在配置文件中的
 private static $_dbConfig = array(
 'host' => '127.0.0.1',
 'username' => 'root',
 'pwd' => '',
 'dbname' => 'bussiness'
 );
 private static $_instance;
 public static function getInstance(){
 if(is_null(self::$_instance)){
  self::$_instance = new mysqli(self::$_dbConfig['host'], self::$_dbConfig['username'], self::$_dbConfig['pwd'], self::$_dbConfig['dbname']);
  if(self::$_instance->connect_errno){
  throw new Exception(self::$_instance->connect_error);
  }
 }
 return self::$_instance;
 }
}

<?php
require_once 'database.php';
class Person extends Database{
 public $instance;
 public $table = 'person';
 public function __construct(){
 $this->instance = Person::getInstance();
 }
 public function getPersonById($personId){
 $sql = "select * from $this->table where id=$personId";
 echo $sql;
 return $this->instance->query($sql);
 }
 /**其他的一些增刪改查操作方法...**/
}

<?php
require_once 'person.php';
$person = new Person();
var_dump($person->getPersonById(1)->fetch_assoc());
die();

select * from person where id=1
array (size=2)
 'id' => string '1' (length=1)
 'name' => string 'ben' (length=3)