In-depth understanding of PHP's MySQL connection class

I accidentally found this Mysql connection class on my computer. I don’t remember where I saved it, so I’ll post it here.
The following methods such as show_databases and show_tables.... all use a lot of echo. It seems that I never like to use output statements directly in class methods, but this only lists the database and table names, and the parameters of the constructor. You can also give a default value.

Copy code The code is as follows:

/*
* filename: mysql database connection class
*/
class mysql{
private $db_host; //Database host
private $db_user; //Database username
private $db_pwd; //Database username and password
private $db_database; //Database name
private $conn; //Database connection identifier;
private $result; //Result resource identification of query command execution
private $sql; //SQL execution statement
private $row; //Number of entries returned
private $coding; //Database encoding, GBK ,UTF8,gb2312
private $bulletin = true; //Whether to enable error logging
private $show_error = true; //During the testing phase, all errors are displayed, which has security risks and is turned off by default
private $is_error = false; //Whether to terminate immediately when an error is detected, the default is true, it is recommended not to enable it, because it is very distressing for users to not see anything when there is a problem
/*Constructor*/
public function __construct($db_host ,$db_user,$db_pwd,$db_database,$conn,$coding){
$this->db_host=$db_host;
$this->db_user=$db_user;
$this-> ;db_pwd = $db_pwd;
$this->db_database=$db_database;
$this->conn=$conn;
$this->coding=$coding;
$this ->connect();
}
/*Database connection*/
public function connect()
{
if($this->conn=="pconn"){
//Permanent link
$this->conn=mysql_pconnect($this->db_host,$this->db_user,$this->db_pwd);
}else{
//Instant link
$this->conn=mysql_connect($this->db_host,$this->db_user,$this->db_pwd);
}
if(!mysql_select_db( $this->db_database,$this->conn)){
if($this->show_error){
$this->show_error("Database is not available:",$this-> ;db_database);
}
}
mysql_query("SET NAMES $this->coding");
}
/*Database execution statements, executable queries, additions, modifications, deletions, etc. sql statement*/
public function query($sql)
{
if($sql == ""){
$this->show_error("sql statement error:","sql The query statement is empty");}
$this->sql = $sql;
$result = mysql_query($this->sql,$this->conn);
if(! $result){
//Used in debugging, it will be automatically printed out when an error occurs in the sql statement
if($this->show_error){
$this->show_error("Error sql statement:" ,$this->sql);
}
}else{
$this->result = $result;
}
return $this->result;
}
/*Create and add a new database*/
public function create_database($database_name){
$database=$database_name;
$sqlDatabase = 'create database '.$database;
$this->query($sqlDatabase);
}
/*Query all databases on the server*/
//Separate the system database and user database for a more intuitive display?
public function show_databases(){
$rs=$this->query("show databases");
echo "Existing database:".$amount =$this->db_num_rows($ rs);
echo "
";
$i=1;
while($row = $this->fetch_array($rs)){
echo "$ i $row[Database]";
echo "
";
$i++;
}
}
//Return all database names in the host in array form
public function databases()
{
$rsPtr=mysql_list_dbs($this->conn);
$i=0;
$cnt=mysql_num_rows($rsPtr);
while($i<$cnt)
{
$rs[]=mysql_db_name($rsPtr,$i);
$i++;
}
return $rs;
}
/*Query all tables under the database*/
function show_tables($database_name){
$this->query("show tables");
echo "Existing database:". $amount = $this->db_num_rows($rs);
echo "
";
$i=1;
while($row = $this->fetch_array( $rs)){
$columnName="Tables_in_".$database_name;
echo "$i $row[$columnName]";
echo "
";
$ i++;
}
}
/*
mysql_fetch_row() array $row[0],$row[1],$row[2]
mysql_fetch_array() array $row[0 ] or $row[id]
mysql_fetch_assoc() array Use $row->content field case sensitivity
mysql_fetch_object() object Use $row[id],$row[content] field case sensitivity
*/
/*Get the result data*/
public function mysql_result_li()
{
return mysql_result($str);
}
/*Get the record set, get the array -Index and association, use $row['content'] */
public function fetch_array()
{
return mysql_fetch_array($this->result);
}
// To get the associative array, use $row['field name']
public function fetch_assoc()
{
return mysql_fetch_assoc($this->result);
}
//Get the number Index array, use $row[0],$row[1],$row[2]
public function fetch_row()
{
return mysql_fetch_row($this->result);
}
//Get the object array, use $row->content
public function fetch_Object()
{
return mysql_fetch_object($this->result);
}
//Simplified query select
public function findall($table)
{
$this->query("SELECT * FROM $table");
}
//Simplified query select
public function select($table,$columnName,$condition)
{
if($columnName==""){
$columnName="*";
}
$this->query("SELECT $columnName FROM $table $condition");
}
//Simplified deletion del
public function delete($table,$condition){
$this ->query("DELETE FROM $table WHERE $condition");
}
//Simplified insertion insert
public function insert($table,$columnName,$value){
$this ->query("INSERT INTO $table ($columnName) VALUES ($value)");
}
//Simplified modification update
public function update($table,$mod_content,$condition) {
$this->query("UPDATE $table SET $mod_content WHERE $condition");
}
/*Get the ID generated by the previous INSERT operation*/
public function insert_id( ){
return mysql_insert_id();
}
//Point to a certain data record
public function db_data_seek($id){
if($id>0){
$id=$id-1;
}
if(!@mysql_data_seek($this->result,$id)){
$this->show_error("The sql statement is incorrect:" , "The specified data is empty");
}
return $this->result;
}
// Calculate the number of result set items based on the select query results
public function db_num_rows( ){
if($this->result==null){
if($this->show_error){
$this->show_error("sql statement error","temporarily Empty, no content!");
   }
   }else{
   return mysql_num_rows($this->result);
   }
}
// 根据insert,update,delete执行结果取得影响行数
public function db_affected_rows(){
   return mysql_affected_rows();
}
//输出显示sql语句
public function show_error($message="",$sql=""){
  if(!$sql){
   echo "".$message."";
   echo "
";
  }else{
   echo "

";
echo "错误信息提示:
";
echo "

";
echo "

";
echo "错误号：12142";
echo "

";
echo "错误原因：".mysql_error()."

";
echo "

";
echo "".$message."";
echo "

";
echo "

".$sql."

";
    $ip=$this->getip();
    if($this->bulletin){
     $time = date("Y-m-d H:i:s");
     $message=$message."/r/n$this->sql"."/r/n客户IP:$ip"."/r/n时间 :$time"."/r/n/r/n";
     $server_date=date("Y-m-d");
     $filename=$server_date.".txt";
     $file_path="error/".$filename;
     $error_content=$message;
     //$error_content="错误的数据库，不可以链接";
     $file = "error"; //设置文件保存目录
     //建立文件夹
     if(!file_exists($file)){
      if(!mkdir($file,0777)){
      //默认的 mode 是 0777，意味着最大可能的访问权
       die("upload files directory does not exist and creation failed");
      }
     }
     //建立txt日期文件
     if(!file_exists($file_path)){
      //echo "建立日期文件";
      fopen($file_path,"w+");
      //首先要确定文件存在并且可写
      if (is_writable($file_path))
      {
       //使用添加模式打开$filename，文件指针将会在文件的开头
       if (!$handle = fopen($file_path, 'a'))
       {
        echo "不能打开文件 $filename";
        exit;
       }
        //将$somecontent写入到我们打开的文件中。
       if (!fwrite($handle, $error_content))
       {
        echo "不能写入到文件 $filename";
        exit;
       }
       //echo "文件 $filename 写入成功";
       echo "——错误记录被保存!";
       //关闭文件
       fclose($handle);
      } else {
       echo "文件 $filename 不可写";
      }
     }else{
      //首先要确定文件存在并且可写
      if (is_writable($file_path))
      {
       //使用添加模式打开$filename，文件指针将会在文件的开头
       if (!$handle = fopen($file_path, 'a'))
       {
        echo "不能打开文件 $filename";
        exit;
       }
        //将$somecontent写入到我们打开的文件中。
       if (!fwrite($handle, $error_content))
       {
        echo "不能写入到文件 $filename";
        exit;
       }
       //echo "文件 $filename 写入成功";
       echo "——错误记录被保存!";
       //关闭文件
       fclose($handle);
      } else {
       echo "文件 $filename 不可写";
      }
     }
    }
    echo "
";
    if($this->is_error){
     exit;
    }
   }
   echo "

";
echo "

";
echo "
";
}
//Release the result set
public function free(){
@mysql_free_result($this->result);
}
//Database selection
public function select_db($db_database){
return mysql_select_db($db_database);
}
//Query the number of fields
public function num_fields($table_name){
//return mysql_num_fields($this->result);
$this->query("select * from $table_name ");
echo "
";
echo "Number of fields: ".$total = mysql_num_fields($this->result);
echo "

"; 
 for ($i=0; $i<$total; $i++){
 print_r(mysql_fetch_field($this->result,$i) );
 }
 echo "< /pre>";
 echo "
";
 }
 //Get MySQL server information
 public function mysql_server($num=''){
 switch ( $num){
 case 1:
 return mysql_get_server_info(); //MySQL server information
 break;
 case 2:
 return mysql_get_host_info(); //Get MySQL host information
 break;
 case 3:
 return mysql_get_client_info(); //Get MySQL client information
 break;
 case 4:
 return mysql_get_proto_info(); //Get MySQL protocol information
 break;
 default:
 return mysql_get_client_info(); //Get mysql version information by default
 }
 }
 //Destructor, automatically close the database, garbage collection mechanism
 public function __destruct()
 {
 if(!empty($this->result)){
 $this->free();
 }
 mysql_close($this ->conn);
 }//function __destruct();
 /*Get the client’s real IP address*/
 function getip(){
 if(getenv("HTTP_CLIENT_IP") && strcasecmp(getenv("HTTP_CLIENT_IP"), "unknown"))
 {
 $ip = getenv("HTTP_CLIENT_IP");
 }
 else if (getenv("HTTP_X_FORWARDED_FOR") && strcasecmp (getenv("HTTP_X_FORWARDED_FOR"), "unknown")){
 $ip = getenv("HTTP_X_FORWARDED_FOR");
 }
 else if (getenv("REMOTE_ADDR") && strcasecmp(getenv("REMOTE_ADDR "), "unknown"))
 {
 $ip = getenv("REMOTE_ADDR");
 }
 else if (isset($_SERVER['REMOTE_ADDR']) && $_SERVER[' REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], "unknown")){
 $ip = $_SERVER['REMOTE_ADDR'];
 }
 else{
 $ip = " unknown";
 }
 return($ip);
 }
}
?>