php class的申明与使用方法

下面来看看在很多程序语言中会使用到的class吧，现在会举个简单的实例来实现php class,类申明,class使用方法哦。

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/*
 * Explorer! 函数库
 * 编写日期：2008-06-29
 * 最后更新：2008-07-18 2:08
 *
 */
class System{//系统部分
 function usr_level($name){
  $SQL = new MySQL();
  $SQL->Query("SELECT `level` FROM `members` WHERE `username` = '$name';");
  $SQL->NextRecord();
  $TMP = $SQL->GetRecord('level');
  $SQL->Free();
  return $TMP;
 }
 function channel_level($cid){
  $SQL = new MySQL();
  $SQL->Query("SELECT `level` FROM `channels` WHERE `id` = $id;");
  $SQL->NextRecord();
  $TMP = $SQL->GetRecord('id');
  $SQL->Free();
  return $TMP;
 }
 function uid2name($uid){
  $SQL = new MySQL();
  if($SQL->Query("SELECT `username` FROM `members` WHERE `uid` = $uid;")){
   $SQL->NextRecord();
   $TMP = $SQL->GetRecord('username');
   $SQL->Free();
   return $TMP;
  }else{
   return 0;
  }
 }
 function name2uid($name){
  $SQL = new MySQL();
  if($SQL->Query("SELECT `uid` FROM `members` WHERE `username` = '$name';")){
   $SQL->NextRecord();
   $TMP = $SQL->GetRecord('uid');
   $SQL->Free();
   return $TMP;
  }else{
   return 0;
  }
 }
 function sysinfo($Name){//获取系统信息
  $SQL = new MySQL();
  $SQL->Query("SELECT * FROM `sysinfo`;");
  $SQL->NextRecord();
  $TMP = $SQL->GetRecord($Name);
  $SQL->Free();
  return $TMP;
 }
 function find_member($name){//查找该用户（注册时需要）
  $SQL = New MySQL();
  $SQL->Query("SELECT * FROM `members` WHERE `username` = '$name';");
  $RS = $SQL->RowS();
  $SQL->Free();
  if($RS)
   return 1;
  else
   return 0;
 }
 function str_safe($str){//字符串安全过滤
  $str = str_replace($str,";","；");
  $str = str_replace($str,"'","‘");
  $str = str_replace($str,"/","／");
  $str = str_replace($str,"`","｀");
  $str = str_replace($str,"\","＼");
  return $str;
 }
 function GetMyIP()
 {
  if ($HTTP_SERVER_VARS["HTTP_X_FORWARDED_FOR"])
   $ip = $HTTP_SERVER_VARS["HTTP_X_FORWARDED_FOR"];
  elseif ($HTTP_SERVER_VARS["HTTP_CLIENT_IP"])
   $ip = $HTTP_SERVER_VARS["HTTP_CLIENT_IP"];
  elseif ($HTTP_SERVER_VARS["REMOTE_ADDR"])
   $ip = $HTTP_SERVER_VARS["REMOTE_ADDR"];
  elseif (getenv("HTTP_X_FORWARDED_FOR"))
   $ip = getenv("HTTP_X_FORWARDED_FOR");
  elseif (getenv("HTTP_CLIENT_IP"))
   $ip = getenv("HTTP_CLIENT_IP");
  elseif (getenv("REMOTE_ADDR"))
   $ip = getenv("REMOTE_ADDR");
  else
   $ip = "127.0.0.1";
  return $ip;
 }
 function Version(){
  return "1.0.9";
 }
}
class MySQL{//数据库部分
 var $DBServer = 'localhost';//服务器
 var $DBName = '';//数据库名称
 var $DBUser = '';//数据库用户
 var $DBPass = '';//数据库密码
 var $OnErrorResume = 1;//错误提示关闭
 var $LinkID = 0;//连接句柄
 var $QueryID = 0;//查询句柄
 var $ResultS = array();//查询结果集
 var $Error = '';//错误信息
 function Connect($Srv = "",$Usr = "",$Pass = "",$DB = ""){//连接数据库
  if($Srv == "") $Srv = $this->DBServer;
  if($Usr == "") $Usr = $this->DBUser;
  if($Pass == "") $Pass = $this->DBPass;
  if($DB == "") $DB = $this->DBName;
  if($this->LinkID == 0){
   $this->LinkID = @mysql_connect($Srv,$Usr,$Pass) or die("数据库连接失败，请联系管理员修复此问题。");
  }
  @mysql_select_db($DB,$this->LinkID) or die("数据库选择失败，请联系管理员修复此问题。");
  return $this->LinkID;
 }
 function Free(){//释放查询结果
  @mysql_free_result($this->QueryID);
  $this->QueryID = 0;
 }
 function RowS(){//查询到的记录总数
  if(!$this->QueryID) return 0;
  return @mysql_num_rows($this->QueryID);
 }
 function NextRecord(){//下一条记录
  if(!$this->QueryID) return 0;
  $this->ResultS = @mysql_fetch_array($this->QueryID);
 }
 function Seek($seek){
  if(!$this->QueryID) return 0;
  @mysql_data_seek($this->QueryID,$seek);
 }
 function Query($Sql){//执行查询
  if($Sql == "") return 0;
  if($this->LinkID == 0) $this->Connect();
  if($this->QueryID) $this->Free();//释放原来查询结果
  $this->QueryID = @mysql_query($Sql,$this->LinkID);
  $this->Error = mysql_error($this->LinkID);
  if(!$this->QueryID) exit("$Sql执行失败."); 
  return $this->QueryID; 
 }
 function GetRecord($Name){
  if(!$this->QueryID) return 0;
  return $this->ResultS[$Name];
 }
}
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