source: trunk/lib/DB.inc.php @ 1

<?php
/**
 * DB.inc.php
 * code by strangecode :: www.strangecode.com :: this document contains copyrighted information
 *
 * DB abstraction layer.
 *
 * @author  Quinn Comendant <quinn@strangecode.com>
 * @version 1.0
 */
 
class DB {

    // If DB::connect has successfully opened a db connection.
    var $_connected = false;

    // Database handler.
    var $dbh;

    // Hash of DB parameters.
    var $_params = array();

    // Default parameters.
    var $_param_defaults = array(

        // DB passwords should be set as apache environment variables in httpd.conf, readable only by root.
        'db_server' => 'localhost',
        'db_name' => null,
        'db_user' => null,
        'db_pass' => null,

        // Debugging.
        'db_always_debug' => false, // TRUE = display all SQL queries.
        'db_debug' => false, // TRUE = display db errors.
        'db_die_on_failure' => false, // TRUE = script stops on db error.
    );
    
    // Translate between HTML and MySQL character set names.
    var $mysql_character_sets = array(
        'utf-8' => 'utf8',
        'iso-8859-1' => 'latin1',
    );
    
    // Caches.
    var $existing_tables;
    var $table_columns;
    
    /**
     * This method enforces the singleton pattern for this class.
     *
     * @return  object  Reference to the global SessionCache object.
     * @access  public
     * @static
     */
    function &getInstance()
    {
        static $instance = null;

        if ($instance === null) {
            $instance = new DB();
        }

        return $instance;
    }
    
    /**
     * Constructor.
     */
    function DB()
    {
        // Initialize default params.
        if (isset($params) && is_array($params)) {
            // Merge new parameters with old overriding only those passed.
            $this->_params = array_merge($this->_params, $params);
        }
    }

    /**
     * Set (or overwrite existing) parameters by passing an array of new parameters.
     *
     * @access public
     *
     * @param  array    $params     Array of parameters (key => val pairs).
     */
    function setParam($params)
    {
        if (!is_a($this, 'DB')) {
            $this =& DB::getInstance();
        }

        if (isset($params) && is_array($params)) {
            // Merge new parameters with old overriding only those passed.
            $this->_params = array_merge($this->_params, $params);
        } else {
            App::logMsg(sprintf('Parameters are not an array: %s', $params), LOG_ERR, __FILE__, __LINE__);
        }
    }

    /**
     * Return the value of a parameter.
     *
     * @access  public
     *
     * @param   string  $param      The key of the parameter to return.
     *
     * @return  mixed               Parameter value.
     */
    function getParam($param)
    {
        if (!is_a($this, 'DB')) {
            $this =& DB::getInstance();
        }

        if (isset($this->_params[$param])) {
            return $this->_params[$param];
        } else {
            App::logMsg(sprintf('Parameter is not set: %s', $param), LOG_DEBUG, __FILE__, __LINE__);
            return null;
        }
    }
    
    /**
     * Connect to database with credentials in params.
     *
     * @access  public
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   28 Aug 2005 14:02:49
     */
    function connect()
    {
        if (!is_a($this, 'DB')) {
            $this =& DB::getInstance();
        }
        
        if (!$this->getParam('db_name') || !$this->getParam('db_user') || !$this->getParam('db_pass')) {
            App::logMsg('Database credentials missing.', LOG_EMERG, __FILE__, __LINE__);
            return false;
        }
        
        // Connect to database. Always create a new link to the server.
        if ($this->dbh = mysql_connect($this->getParam('db_server'), $this->getParam('db_user'), $this->getParam('db_pass'), true)) {    
            // Select database
            mysql_select_db($this->getParam('db_name'), $this->dbh);
        }
        
        // Connection errors.
        if (!$this->dbh || mysql_error($this->dbh)) {
            $mysql_error_msg = $this->dbh ? 'Codebase MySQL error: (' . mysql_errno($this->dbh) . ') ' . mysql_error($this->dbh) : 'Codebase MySQL error: Could not connect to server.';
            if ($this->getParam('db_debug')) {
                echo $mysql_error_msg . "\n";
            } else {
                echo _("This page is temporarily unavailable. It should be back up in a few minutes.");
            }
            App::logMsg($mysql_error_msg, LOG_EMERG, __FILE__, __LINE__);
            echo "\n\n<!-- Script execution stopped out of embarrassment. -->";
            die;
        }
        
        // DB connection success!
        $this->_connected = true;

        // Set the character set used for communicating with MySQL.
        $this->query("SET NAMES '" . $this->mysql_character_sets[strtolower(App::getParam('character_set'))] . "'");
        
        return true;
    }
    
    /**
     * Close db connection.
     *
     * @access  public
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   28 Aug 2005 14:32:01
     */
    function close()
    {
        if (!is_a($this, 'DB')) {
            $this =& DB::getInstance();
        }
        
        if (!$this->_connected) {
            return false;
        }

        mysql_close($this->dbh);        
    }
    
    /**
     * Return the current database handler.
     *
     * @access  public
     * @return  resource Current value of $this->dbh.
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   20 Aug 2005 13:50:36
     */
    function getDBH()
    {
        if (!is_a($this, 'DB')) {
            $this =& DB::getInstance();
        }
        
        if (!$this->_connected) {
            return false;
        }

        return $this->dbh;
    }
    
    /**
     * Returns connection status
     *
     * @access  public
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   28 Aug 2005 14:58:09
     */
    function isConnected()
    {
        return $this->_connected;
    }
    
    /**
     * A wrapper for mysql_query. Allows us to set the database link_identifier,
     * to trap errors and ease debugging.
     *
     * @param  string  $query   The SQL query to execute
     * @param  bool    $debug   If true, prints debugging info
     * @return resource         Query identifier
     */
    function query($query, $debug=false)
    {
        static $_query_count = 0;
        
        if (!is_a($this, 'DB')) {
            $this =& DB::getInstance();
        }
        
        if (!$this->_connected) {
           return false;
        }

        $_query_count++;
        $debugqry = preg_replace("/\n[\t ]+/", "\n", $query);
        if ($this->getParam('db_always_debug') || $debug) {
            echo "<!-- ----------------- Query $_query_count ---------------------\n$debugqry\n-->\n";
        }
        
        // Execute!
        $qid = mysql_query($query, $this->dbh);
    
        // Error checking.
        if (!$qid || mysql_error($this->dbh)) {
            if ($this->getParam('db_debug')) {
                echo '<pre style="padding:2em; background:#ddd; font:9px monaco;">' . wordwrap(mysql_error($this->dbh)) . '<hr>' . htmlspecialchars($debugqry) . '</pre>';
            } else {
                echo _("This page is temporarily unavailable. It should be back up in a few minutes.");
            }
            App::logMsg(sprintf('MySQL error %s: %s in query: %s', mysql_errno($this->dbh), mysql_error($this->dbh), $debugqry), LOG_EMERG, __FILE__, __LINE__);
            if ($this->getParam('db_die_on_failure')) {
                echo "\n\n<!-- Script execution stopped out of embarrassment. -->";
                die;
            }
        }
    
        return $qid;
    }

    /**
     * Loads a list of tables in the current database into an array, and returns 
     * true if the requested table is found. Use this function to enable/disable
     * funtionality based upon the current available db tables or to dynamically 
     * create tables if missing.
     *
     * @param  string $table    The name of the table to search.
     * @param  bool   $strict   Get fresh table info (in case DB changed).
     * @return bool    true if given $table exists.
     */
    function tableExists($table, $use_cached_results=true)
    {   
        if (!is_a($this, 'DB')) {
            $this =& DB::getInstance();
        }
        
        if (!$this->_connected) {
            return false;
        }

        if (!isset($this->existing_tables) || !$use_cached_results) {
            $this->existing_tables = array();
            $qid = $this->query("SHOW TABLES");
            while (list($row) = mysql_fetch_row($qid)) {
                $this->existing_tables[] = $row;
            }
        }
        if (in_array($table, $this->existing_tables)) {
            return true;
        } else {
            App::logMsg(sprintf('nonexistent DB table: %s.%s', $this->getParam('db_name'), $table), LOG_ALERT, __FILE__, __LINE__);
            return false;
        }
    }
    
    /**
     * Tests if the given array of columns exists in the specified table.
     *
     * @param  string $table    The name of the table to search.
     * @param  array  $columns  An array of column names.
     * @param  bool   $strict   Exact schema match, or are additional fields in the table okay?
     * @param  bool   $strict   Get fresh table info (in case DB changed).
     * @return bool    true if given $table exists.
     */
    function columnExists($table, $columns, $strict=true, $use_cached_results=true)
    {   
        if (!is_a($this, 'DB')) {
            $this =& DB::getInstance();
        }
        
        if (!$this->_connected) {
            return false;
        }

        // Ensure the table exists.
        if (!$this->tableExists($table, $use_cached_results)) {
            return false;
        }
        
        // For single-value columns.
        if (!is_array($columns)) {
            $columns = array($columns);
        }
        
        if (!isset($this->table_columns[$table]) || !$use_cached_results) {
            // Populate and cache array of current columns for this table.
            $this->table_columns[$table] = array();
            $qid = $this->query("DESCRIBE $table");
            while ($row = mysql_fetch_row($qid)) {
                $this->table_columns[$table][] = $row[0];
            }
        }
    
        if ($strict) {
            // Do an exact comparison of table schemas.
            sort($columns);
            sort($this->table_columns[$table]);
            return $this->table_columns[$table] == $columns;
        } else {
            // Only check that the specified columns are available in the table.
            $match_columns = array_intersect($this->table_columns[$table], $columns);
            sort($columns);
            sort($match_columns);
            return $match_columns == $columns;
        }
    }
    
    /**
     * Reset cached items.
     *
     * @access  public
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   28 Aug 2005 22:10:50
     */
    function resetCache()
    {
        $this->existing_tables = null;
        $this->table_columns = null;
    }
    
} // End.

?>