如何通过php实现Mysql简易操作？

<?php
class mysql extends PDO{
 public $server;
 public $database;
 public $user;
 public $password;
 public $sql;
 public function __construct($server,$database,$user,$password,$port=3306){
  $this->server = $server;
  $this->database = $database;
  $this->user = $user;
  $this->password = $password;
  parent::__construct("mysql:host=$server;port=$port;dbname=$database",$user,$password);
  $this->query('SET NAMES utf8');
 }
 public function drop($table){
  $sql = 'DROP TABLE '.$table.';';
  $re = $this->query($sql);
  if($re){
   return true;
  }else{
   return false;
  }
 }
 public function insert($table,$name,$value=null){
  $sql = "INSERT INTO ".$table.'(';
  if($value == null){
  $arrname = array_keys($name);
  $arrvalue = array_values($name);
  }else{
  $arrname = explode('|', $name);
  $arrvalue = explode('|', $value);
  }
  for($i=0;$i<count($arrname);$i++){
   if($i==count($arrname)-1){
    $sql = $sql.$arrname[$i];
   }else{
    $sql = $sql.$arrname[$i].",";
   }
  }
  $sql = $sql.")VALUES(";
  for($i=0;$i<count($arrvalue);$i++){
   if($i==count($arrvalue)-1){
    $sql = $sql."'".$arrvalue[$i]."'";
   }else{
    $sql = $sql."'".$arrvalue[$i]."',";
   }
  }
  $sql .=");";
  $re = $this->query($sql);
  if($re){
   return true;
  }else{
   return false;
  }
 }
 public function delete($table,$Conditionsname,$Conditionsvalue=null){
  if($Conditionsvalue!=null){
   $sql = "DELETE FROM ".$table." WHERE ".$Conditionsname."='".$Conditionsvalue."';";
  }else{
   $sql = "DELETE FROM ".$table." WHERE ";
   $arrname = array_keys($Conditionsname);
   $arrvalue = array_values($Conditionsname);
   for($i=0;$i<count($arrname);$i++){
    if($i==count($arrname)-1){
     $sql.=$arrname[$i].'='."'".$arrvalue[$i]."'";
    }else{
     $sql.=$arrname[$i].'='."'".$arrvalue[$i]."',";
    }
   }
   $sql.=';';
  }
  $re = $this->query($sql);
  if($re){
   return true;
  }else{
   return false;
  }
 }
 public function select($table,$name,$Conditionsname,$Conditionsvalue=null){
  if($Conditionsvalue!=null){
   $sql = "SELECT ".$name." FROM ".$table." WHERE ".$Conditionsname."='".$Conditionsvalue."';";
  }else{
   $sql = "SELECT ".$name." FROM ".$table." WHERE ";
   $arrname = array_keys($Conditionsname);
   $arrvalue = array_values($Conditionsname);
   for($i=0;$i<count($arrname);$i++){
    if($i==count($arrname)-1){
     $sql.=$arrname[$i].'='."'".$arrvalue[$i]."'";
    }else{
     $sql.=$arrname[$i].'='."'".$arrvalue[$i]."' and ";
    }
   }
   $sql.=';';
  }
  $re = $this->query($sql);
  $row = $re->fetch();
  return $row[$name];
 }
 public function update($table,$name,$value,$Conditionsname,$Conditionsvalue=null){
  if($Conditionsvalue!=null){
   $sql = "UPDATE ".$table." SET ".$name."= '".$value."' WHERE ".$Conditionsname."='".$Conditionsvalue."';";
  }else{
   $sql = "UPDATE ".$table." SET ".$name."= '".$value."' WHERE ";
   $arrname = array_keys($Conditionsname);
   $arrvalue = array_values($Conditionsname);
   for($i=0;$i<count($arrname);$i++){
    if($i==count($arrname)-1){
     $sql.=$arrname[$i].'='."'".$arrvalue[$i]."'";
    }else{
     $sql.=$arrname[$i].'='."'".$arrvalue[$i]."' and ";
    }
   }
   $sql.=';';
  }
  $re = $this->query($sql);
  if($re){
   return true;
  }else{
   return false;
  }
 }
 public function group($table,$name){
  $sql = "SELECT ".$name." FROM ".$table.";";
  $return = array();
  $re = $this->query($sql);
  while($row = $re->fetch(PDO::FETCH_ASSOC)){
   array_push($return,$row[$name]);
  }
  return $return;
 }
 public function fetchall($sql){
  $return = array();
  $re = $this->query($sql);
  while($row = $re->fetch(PDO::FETCH_ASSOC)){
   array_push($return,$row);
  }
  return $return;
 }
}