MySQL Data backup class code

 /***
  * Description, this class is suitable for small Web site database tutorial backup, built-in MySQL connection, simply configure the data connection
  * and storage backup location. The Show_dir_file () method in the
  * class can return directly to all files in the backup directory, and returns an array form
  * Method Expord_sql () directly generate SQL files
  * This kind of production is simple and can be spread arbitrarily , how do you propose to this class, please send a message to the shrimp
  * Producer: Tour Day Shrimp
  * emial:328742379@qq.com
  * **/

Class Data {
 public   $data _dir    = "class/";      // The path to which the backup file is stored
 public   $data _name   = "111cnnet.sql";    //backup file name
  private  $mysql _host  = "localhost"     //database address
 private  $mysql _user   = "root";      //user name
 private  $mysql _pwd   = "lpl19881129";     //password
 private  $mysql _db    = "Date";      //database name
 private  $mysql _code  = "GBK";       //encoding method

/***
* 1. Connecting to the database
* **/
function __construct () {
$conn = mysql_connect ($this->mysql_host, $this->mysql_user, $this->mysql_pwd);
mysql_select_db ($this->mysql_db);
mysql_query ("Set names $this->mysql_code");
}

/***
* 2. Generate SQL statements
* **/
Private Function Set_sql ($table) {
$tabledump = "DROP table if exists $table;";
$createtable = mysql_query ("Show create Table $table");
$create = Mysql_fetch_row ($createtable);
$tabledump. = $create [1]. ";";

$rows = mysql_query ("SELECT * from $table");
$numfields = Mysql_num_fields ($rows);
$numrows = mysql_num_rows ($rows);
while ($row = Mysql_fetch_row ($rows)) {
$comma = "";
$tabledump. = "INSERT into $table values (";
for ($i = 0; $i < $numfields; $i + +)
{
$tabledump. = $comma. "'". Mysql_escape_string ($row [$i]). "'";
$comma = ",";
}
$tabledump. = ");";
}
$tabledump. = "";

return $tabledump;
}

/***
* 3. Display files that have been backed up under the storage directory
* **/
Public Function Show_dir_file () {
$dir = $this->data_dir;
if (!is_dir ($dir)) {
if (!mkdir ($dir)) {
Echo folder does not exist, try to create a folder, create a failure, maybe you do not have relevant permissions ";
Exit ();
}else{
chmod ($dir, 755);
}
}

if (!is_writable ($dir)) {
echo "File not writable";
Exit ();
}

$link = Opendir ($dir);
if (! $link) {
echo "Create link Failed";
Exit ();
}
Return Scandir ($dir);
}

/***
* 4. Generate SQL file
* **/
Public Function Expord_sql () {
$this->show_dir_file ();
$result = Mysql_list_tables ($this->mysql_db);
while ($arr = Mysql_fetch_row ($result)) {
$tables. = $this->set_sql ($arr [0]);
}
$file = $this->data_dir. $this->data_name;
$link = fopen ($file, "w+");
if (!is_writable ($file)) {
echo "File not writable";
Exit ();
}
Fwrite ($link, $tables);
Fclose ($link);
echo "Backup succeeded";
}

}