A useful php mysql connection class

This article shares a useful PHP and MySQL operation class. The difference between this MySQL class and other classes is that it can set read and write locks on the table. Friends in need can refer to it.

Share a php and mysql operation class, code:

<?php
/**
* mysql操作类
* by bbs.it-home.org
*/

// 定义常量

/**
 * 是否开启调试模式
 */
define("DEBUG", FALSE);

/**
 * 以下变量不要改动
 */

/**
 * 设定表的读锁
 */
define("LOCKED_FOR_READ", "READ");
/**
 * 设定表的写锁
 */
define("LOCKED_FOR_WRITE", "WRITE");

/**
 * HOWTO
 */
class mySQL {

 /**
    * The connection resource id
    *
    * @var  object
    */
 var $connection;

 /**
    * The selected database
    *
    * @var  object
    */
 var $selectedDb;

 /**
    * The result from a select-query
    *
    * @var  object
    */
 var $result;

 /**
    * Flag that tells if you are connected to the database or not
    *
    * @var  boolean
    */
 var $isConnected;

 /**
    * Flag that tells if you the tables are locked or not
    *
    * @var  boolean
    */
 var $isLocked;
 
 /**
  *This will indicate what querytype the last query was
  *
  * @var string
  */
 var $queryType;

 /**
  * This is the constructor of this mysql class.
  * It creates a connection to the database, and if possible it sets the database to
  * You can specify if you want to use persistant connections or not.
  *
  * @param  string The host to the mySQL server
  * @param string The username you use to log on to the mySQL server
  * @param string The password you use to log on to the mySQL server
  * @param string The name of the database you wish to use
  * @param boolean TRUE if you want to use persistant connections. Default is TRUE
  * @return boolean TRUE when connection was successfull
  * @access public
  */ 
 function mySQL($sHost, $sUser, $sPassword, $sDatabase="", $bPersistant=TRUE) {
  $conFunc = "";
  
  if(!defined("DEBUG")) {
   define("DEBUG", FALSE);
  }
  
  if($this->getConnected()) {
   $this->closeConnection();
  }
  if($this->connection = ($bPersistant ? mysql_pconnect($sHost, $sUser, $sPassword) : mysql_connect($sHost, $sUser, $sPassword))) {
   $this->setConnected(TRUE);
   
   if($sDatabase) {
    $this->setDb($sDatabase);
   
   }
   
   return TRUE;
  } else {
   $this->setConnected(FALSE);
   return FALSE;
  }
 }
 
 /**
  * This is the destructor of this class. It frees the result of a query,
  * it unlocks all locked tables and close the connection to the database
  * It does not return anything at all, so you will not know if it was sauccessfull
  *
  * @access public
  */
 function _mySQL() {
  if($this->result) {
   $this->freeResult();
  }
  if($this->getLocked()) {
   $this->unlock();
  }
  if($this->getConnected()) {
   $this->closeConnection();
  }
 }
 
 /**
  * This function frees the result from a query if there is any result.
  *
  * @access public
  */
 function freeResult() {
  if($this->result) {
   @mysql_free_result($this->result);
  }
 }
 
 /**
  * This function executes a query to the database.
  * The function does not return the result of the query, you must call the
  * function getQueryResult() to fetch the result
  *
  * @param  string The query-string to execute
  * @return boolean TRUE if the query was successfull
  * @access public
  */
 function query($query) {
  if(strlen(trim($query)) == 0) {
   $this->printError("No query got in function query()");
   return FALSE;
  }
  if(!$this->getConnected()) {
   $this->printError("Not connected in function query()");
   return FALSE;
  }
  
  $queryType = substr(trim($query), 0, strpos($query, " "));
  $this->setQueryType($queryType);
  
  $this->result = mysql_query($query, $this->connection);
  if($this->result) {
   return TRUE;
  }
  return FALSE;
 }
 
 /**
  * Sets the querytype of the last query executed
  * For example it can be SELECT, UPDATE, DELETE etc.
  *
  * @access private
  */
 function setQueryType($type) {
  $this->queryType = strtoupper($type);
 }
 
 /**
  * Returns the querytype
  *
  * @return string
  * @access private
  */
 function getQueryType() {
  return $this->queryType;
 }
 
 /**
  * This function returns number of rows got when executing a query
  *
  * @return mixed FALSE if there is no query-result.
  *     If the queryType is SELECT then it will use the function MYSQL_NUM_ROWS
  *     Otherwise it uses the MYSQL_AFFECTED_ROWS
  * @access public
  */
 function getNumRows() {
  if($this->result) {
   if(DEBUG==TRUE) {
    print("<font style=\"background-color: red\">".$this->getQueryType()."</font><br>");
   }
   return mysql_affected_rows($this->connection);
  }
  return FALSE;
 }
 
 /**
  * The function returns the result from a call to the query() function
  *
  * @return object
  * @access public
  */
 function getQueryResult() {
  return $this->result;
 }
 
 /**
  * This function returns the query result as an array for each row in the query result
  *
  * @return array
  * @access public
  */
 function fetchArray() {
  if($this->result) {
   return mysql_fetch_array($this->result);
  }
  return FALSE;
 }
 
 /**
  * This function returns the query result as an object for each row in the query result
  *
  * @return object
  * @access public
  */
 function fetchObject() {
  if($this->result) {
   return mysql_fetch_object($this->result);
  }
  return FALSE;
 }
 
 /**
  * This function returns the query result as an array for each row in the query result
  *
  * @return array
  * @access public
  */
 function fetchRow() {
  if($this->result) {
   return mysql_fetch_row($this->result);
  }
  return FALSE;
 }
 
 /**
  * This function sets the database
  *
  * @return boolean TRUE if the database was set
  * @access public
  */
 function setDb($sDatabase) {
  if(!$this->getConnected()) {
   $this->printError("Not connected in function setDb()");
   return FALSE;
  }
  if($this->selectedDb = mysql_select_db($sDatabase, $this->connection)) {
   return TRUE;
  }
  return FALSE;
 }
 
 /**
  * This function returns a flag so you can see if you are connected to the database
  * or not
  *
  * @return boolean TRUE when connected to the database
  * @access public
  */
 function getConnected() {
  return $this->isConnected;
 }

 /**
  * This function sets the flag so you can see if you are connected to the database
  *
  * @param $bStatus The status of the connection. TRUE if you are connected,
  *      FALSE if you are not
  * @access public
  */
 function setConnected($bStatus) {
  $this->isConnected = $bStatus;
 }
 
 /**
  * The function unlocks tables if there are locked tables and the closes the
  * connection to the database.
  *
  * @access public
  */
 function closeConnection() {
  if($this->getLocked()) {
   $this->unlock();
  }
  
  if($this->getConnected()) {
   mysql_close($this->connection);
   $this->setConnected(FALSE);
  }
 }
 
 /**
  * Unlocks all tables that are locked
  *
  * @access public
  */
 function unlock() {
  if(!$this->getConnected()) {
   $this->setLocked(FALSE);
  }   
  if($this->getLocked()) {
   $this->query("UNLOCK TABLES"); 
   $this->setLocked(FALSE);
  }
 }

 /**
  * This function locks the table(s) that you specify
  * The type of lock must be specified at the end of the string.
  *
  * @param string a string containing the table(s) to lock, 
  *     as well as the type of lock to use (READ or WRITE) 
  *     at the end of the string
  * @return boolean TRUE if the tables was successfully locked
  * @access private
  */
 function lock($sCommand) {
  if($this->query("LOCK TABLE ".$sCommand)) {
   $this->setLocked(TRUE);
   return TRUE;
  }
  
  $this->setLocked(FALSE);
  return FALSE;
 }
 
 /**
  * This functions sets read lock to specified table(s)
  *
  * @param string a string containing the table(s) to read-lock
  * @return boolean TRUE on success
  */
 function setReadLock($sTable) {
  return $this->lock($sTable." ".LOCKED_FOR_READ);
 }
 
 /**
  * This functions sets write lock to specified table(s)
  *
  * @param string a string containing the table(s) to read-lock
  * @return boolean TRUE on success
  */
 function setWriteLock($sTable) {
  return $this->lock($sTable." ".LOCKED_FOR_WRITE);
 }
  
 /**
  * Sets the flag that indicates if there is any tables locked
  *
  * @param boolean The flag that will indicate the lock. TRUE if locked
  */
 function setLocked($bStatus) {
  $this->isLocked = $bStatus;
 }
 
 /**
  * Returns TRUE if there is any locked tables
  *
  * @return boolean TRUE if there are locked tables
  */
 function getLocked() {
  return $this->isLocked;
 }

 /**
  * Prints an error to the screen. Can be used to kill the application
  *
  * @param string The text to display
  * @param boolean TRUE if you want to kill the application. Default is FALSE
  */
 function printError($text, $killApp=FALSE) {
  if($text) {
   print("<b>Error</b><br />".$text);
  }
  if($killApp) {
   exit();
  }
 }
 
 /**
  * Display any mysql-error
  *
  * @return mixed String with the error if there is any error.
  *     Otherwise it returns FALSE
  */
 function getMysqlError() {
  if(mysql_error()) {
   return "<br /><b>Mysql Error Number ".mysql_errno()."</b><br />".mysql_error();
  }
  return FALSE;
 }
}
?>