source: branches/eli_branch/lib/DB.inc.php @ 439

<?php
/**
 * The Strangecode Codebase - a general application development framework for PHP
 * For details visit the project site: <http://trac.strangecode.com/codebase/>
 * Copyright 2001-2012 Strangecode, LLC
 * 
 * This file is part of The Strangecode Codebase.
 *
 * The Strangecode Codebase is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your option)
 * any later version.
 * 
 * The Strangecode Codebase is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * The Strangecode Codebase. If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * DB.inc.php
 *
 * Very lightweight DB semi-abstraction layer. Mainly to catch errors with mysql_query, with some goodies.
 *
 * @author  Quinn Comendant <quinn@strangecode.com>
 * @version 2.1
 */

class DB {

    // If $db->connect has successfully opened a db connection.
    private $_connected = false;

    // Database handle.
    public $dbh;
    
    // Count how many queries run during the whole instance.
    private $_query_count = 0;

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

    // Default parameters.
    private $_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,

        // Display all SQL queries. FALSE recommended for production sites.
        'db_always_debug' => false,

        // Display db errors. FALSE recommended for production sites.
        'db_debug' => false,
        
        // Script stops on db error. TRUE recommended for production sites.
        'db_die_on_failure' => true,
    );

    // Translate between HTML and MySQL character set names.
    public $mysql_character_sets = array(
        'utf-8' => 'utf8',
        'iso-8859-1' => 'latin1',
    );

    // Caches.
    public $existing_tables;
    public $table_columns;

    /**
     * This method enforces the singleton pattern for this class.
     *
     * @return  object  Reference to the global DB object.
     * @access  public
     * @static
     */
    public static function &getInstance()
    {
        static $instance = null;

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

        return $instance;
    }

    /**
     * Set (or overwrite existing) parameters by passing an array of new parameters.
     *
     * @access public
     *
     * @param  array    $params     Array of parameters (key => val pairs).
     */
    public function setParam($params)
    {
        $app =& App::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, if it exists.
     *
     * @access public
     * @param string $param        Which parameter to return.
     * @return mixed               Configured parameter value.
     */
    public function getParam($param)
    {
        $app =& App::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
     */
    public function connect()
    {
        $app =& App::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);
        }

        // Test for 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.';
            $app->logMsg($mysql_error_msg, LOG_EMERG, __FILE__, __LINE__);

            // Print helpful or pretty error?
            if ($this->getParam('db_debug')) {
                echo $mysql_error_msg . "\n";
            }

            // Die if db_die_on_failure = true, or just continue without connection.
            return $this->_fail();
        }

        // DB connection success!
        $this->_connected = true;

        // Tell MySQL what character set we're using. Available only on MySQL versions > 4.01.01.
        if ('' != $app->getParam('character_set') && isset($this->mysql_character_sets[mb_strtolower($app->getParam('character_set'))])) {
            $this->query("/*!40101 SET NAMES '" . $this->mysql_character_sets[mb_strtolower($app->getParam('character_set'))] . "' */");
        } else {
            $app->logMsg(sprintf('%s is not a known character_set.', $app->getParam('character_set')), LOG_ERR, __FILE__, __LINE__);
        }

        return true;
    }

    /**
     * Close db connection.
     *
     * @access  public
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   28 Aug 2005 14:32:01
     */
    public function close()
    {
        if (!$this->_connected) {
            return false;
        }
        $this->_connected = false;
        return mysql_close($this->dbh);
    }
    
    /*
    * 
    *
    * @access   public
    * @param    
    * @return   
    * @author   Quinn Comendant <quinn@strangecode.com>
    * @version  1.0
    * @since    03 Jul 2013 14:50:23
    */
    public function reconnect()
    {
        $this->close();
        $this->connect();
    }
    
    /*
    * Die only if db_die_on_failure is true. This will be set to false for some cases
    * when a database is not required for web app functionality.
    *
    * @access   public
    * @param    string  $msg Print $msg when dying.
    * @return   bool    false If we don't die.
    * @author   Quinn Comendant <quinn@strangecode.com>
    * @version  1.0
    * @since    15 Jan 2007 15:59:00
    */
    private function _fail()
    {
        if ($this->getParam('db_die_on_failure')) {
            header(' ', true, 503);
            echo _("This page is temporarily unavailable. Please try again in a few minutes.");
            die;
        } else {
            return false;
        }
    }

    /**
     * Return the current database handler.
     *
     * @access  public
     * @return  resource Current value of $this->dbh.
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   20 Aug 2005 13:50:36
     */
    public function getDBH()
    {
        if (!$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
     */
    public function isConnected()
    {
        return (true === $this->_connected);
    }
    
    /**
     * Returns a properly escaped string using mysql_real_escape_string() with the current connection's charset.
     *
     * @access  public
     * @param   string  $string     Input string to be sent as SQL query.
     * @return  string              Escaped string from mysql_real_escape_string()
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   06 Mar 2006 16:41:32
     */
    public function escapeString($string)
    {
        if (!$this->_connected) {
            return false;
        }

        return mysql_real_escape_string($string, $this->dbh);
    }

    /**
     * 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    $debug   If true, prints debugging info
     * @return resource         Query identifier
     */
    public function query($query, $debug=false)
    {    
        $app =& App::getInstance();

        if (!$this->_connected) {
           return false;
        }

        $this->_query_count++;

        $debugqry = preg_replace("/\n[\t ]+/", "\n", $query);
        if ($this->getParam('db_always_debug') || $debug) {
            echo "<!-- ----------------- Query $this->_query_count ---------------------\n$debugqry\n-->\n";
        }
        
        // Ensure we have an active connection. 
        // If we continue on a dead connection we might experience a "MySQL server has gone away" error.
        // http://dev.mysql.com/doc/refman/5.0/en/gone-away.html
        if (!mysql_ping($this->dbh)) {
            $app->logMsg(sprintf('MySQL ping failed; reconnecting
 ("%s")', truncate(trim($debugqry), 150)), LOG_NOTICE, __FILE__, __LINE__);
            $this->reconnect();
        }

        // Execute!
        $qid = mysql_query($query, $this->dbh);

        // Error checking.
        if (!$qid || mysql_error($this->dbh)) {
            $app->logMsg(sprintf('MySQL error %s: %s in query: %s', mysql_errno($this->dbh), mysql_error($this->dbh), $debugqry), LOG_EMERG, __FILE__, __LINE__);
            if ($this->getParam('db_debug')) {
                echo '<pre style="padding:2em; background:#ddd; font:9px monaco;">' . wordwrap(mysql_error($this->dbh)) . '<hr>' . htmlspecialchars($debugqry) . '</pre>';
            }            
            // Die if db_die_on_failure = true, or just continue without connection
            return $this->_fail();
        }

        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
     * functionality 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   $use_cached_results   Get fresh table info (in case DB changed).
     * @return bool                         true if given $table exists.
     */
    public function tableExists($table, $use_cached_results=true)
    {
        $app =& App::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   $use_cached_results   Get fresh table info (in case DB changed).
     * @return bool                         true if column(s) exist.
     */
    public function columnExists($table, $columns, $strict=true, $use_cached_results=true)
    {
        if (!$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;
        }
    }
    
    /*
    * Return the total number of queries executed thus far.
    *
    * @access   public
    * @return   int Number of queries
    * @author   Quinn Comendant <quinn@strangecode.com>
    * @version  1.0
    * @since    15 Jun 2006 11:46:05
    */
    public function numQueries()
    {
        return $this->_query_count;
    }

    /**
     * Reset cached items.
     *
     * @access  public
     * @author  Quinn Comendant <quinn@strangecode.com>
     * @since   28 Aug 2005 22:10:50
     */
    public function resetCache()
    {
        $this->existing_tables = null;
        $this->table_columns = null;
    }

} // End.