Attempting to write a class that can be used to abstract the database that is being used within a php application. Currently supports mysqli and sqlite.

DatabaseUtilities.php

<?php

class DatabaseUtility {

  /**
   * Opens the connection to the database and returns the database handler.
   *
   * @param $db_server - the name of the server that hosts the database
   * @param $db_user - the name of the user to use to access the database
   * @param $db_password - the password for the user to access the database
   * @param $db_database - the name of the database to connect to
   */
  public function open($db_server, $db_user, $db_password, $db_database) {
    echo 'use the real implementation instead of the base class';
  }

  /**
   * Queries the database using the query parameter and returns the results
   *
   * @param $db_handle - the handle for the database connection
   * @param $query - the query to execute
   */
  public function query($db_handle, $query) {
    echo 'use the real implementation instead of the base class';
  }

  /**
   * Inserts data into the database.
   *
   * @param $db_handle - the handle for the database connection
   * @param $statement - the SQL statement to execute
   */
  public function insert($db_handle, $statement) {
    echo 'use the real implementation instead of the base class';
  }

  /**
   * Gets the last inserted rows id.
   *
   * @param $db_handle - the handle for the database connection
   * @returns the last inserted rows id
   */
  public function getInsertId($db_handle) {
    echo 'use the real implementation instead of the base class';
  }

  /**
   * Gets the last error message for the most recent function call to succeed or fail.
   *
   * @param $db_handle - the handle for the database
   * @returns the last error message for the most recent function call to succeed or fail
   */
  public function getError($db_handle) {
    echo 'use the real implementation instead of the base class';
  }

  /**
   * Fetches the next row that is represented in the result object.
   *
   * @param $result - the result of a query call
   * @returns the next row in the result
   */
  public function getRow($result) {
    echo 'use the real implementation instead of the base class';
  }

  /**
   * Frees the result set
   *
   * @param $result - the result set to free
   */
  public function freeResult($result) {
    echo 'use the real implementation instead of the base class';
  }

  /**
   * Gets the number of rows that were affected by the most recent function call.
   *
   * @param $result - the result set to check
   * @returns the number of rows affected
   */
  public function numberOfRowsAffected($result) {
    echo 'use the real implementation instead of the base class';
  }
}

class MySQLDatabaseUtility extends DatabaseUtility {

  /**
   * Opens the connection to the database and returns the database handler.
   *
   * @param $db_server - the name of the server that hosts the database
   * @param $db_user - the name of the user to use to access the database
   * @param $db_password - the password for the user to access the database
   * @param $db_database - the name of the database to connect to
   */
  public function open($db_server, $db_user, $db_password, $db_database) {
    $handle = new mysqli($db_server, $db_user, $db_password, $db_database);
    if ($handle->connect_errno) {
      die("Could not connect to the database - " . $handle->connect_errno);
    }
    return $handle;
  }

  /**
   * Queries the database using the query parameter and returns the results
   *
   * @param $db_handle - the handle for the database connection
   * @param $query - the query to execute
   */
  public function query($db_handle, $query) {
    return $db_handle->query($query);
  }

  /**
   * Inserts data into the database.
   *
   * @param $db_handle - the handle for the database connection
   * @param $statement - the SQL statement to execute
   */
  public function insert($db_handle, $statement) {
    $db_handle->query($statement);
  }

  /**
   * Gets the last inserted rows id.
   *
   * @param $db_handle - the handle for the database connection
   * @returns the last inserted rows id
   */
  public function getInsertId($db_handle) {
    return $db_handle->insert_id;
  }

  /**
   * Gets the last error message for the most recent function call to succeed or fail.
   *
   * @param $db_handle - the handle for the database
   * @returns the last error message for the most recent function call to succeed or fail
   */
  public function getError($db_handle) {
    return $db_handle->error;
  }

  /**
   * Fetches the next row that is represented in the result object.
   *
   * @param $result - the result of a query call
   * @returns the next row in the result
   */
  public function getRow($result) {
    return $result->fetch_array();
  }

  /**
   * Frees the result set
   *
   * @param $result - the result set to free
   */
  public function freeResult($result) {
    $result->free();
  }

  /**
   * Gets the number of rows that were affected by the most recent function call.
   *
   * @param $result - the result set to check
   * @returns the number of rows affected
   */
  public function numberOfRowsAffected($result) {
    return $result->num_rows;
  }
}

class SQLiteDatabaseUtility extends DatabaseUtility {

  /**
   * Opens the connection to the database and returns the database handler.
   *
   * @param $db_server - not used
   * @param $db_user - not used
   * @param $db_password - not used
   * @param $db_database - the location of the database to connect to
   */
  public function open($db_server, $db_user, $db_password, $db_database) {
    $handle = sqlite_open($db_database, 0666, $error);
    if (!$handle) {
      die("Could not connect to the database - " . $error);
    }
    return $handle;
  }

  /**
   * Queries the database using the query parameter and returns the results
   *
   * @param $db_handle - the handle for the database connection
   * @param $query - the query to execute
   */
  public function query($db_handle, $query) {
    return sqlite_query($db_handle, $query);
  }

  /**
   * Inserts data into the database.
   *
   * @param $db_handle - the handle for the database connection
   * @param $statement - the SQL statement to execute
   */
  public function insert($db_handle, $statement) {
    sqlite_exec($db_handle, $statement);
  }

  /**
   * Gets the last inserted rows id.
   *
   * @param $db_handle - the handle for the database connection
   * @returns the last inserted rows id
   */
  public function getInsertId($db_handle) {
    return sqlite_last_insert_rowid($db_handle);
  }

  /**
   * Gets the last error message for the most recent function call to succeed or fail.
   *
   * @param $db_handle - the handle for the database
   * @returns the last error message for the most recent function call to succeed or fail
   */
  public function getError($db_handle) {
    $code = sqlite_last_error($db_handle);
    return sqlite_error_string($code);
  }

  /**
   * Fetches the next row that is represented in the result object.
   *
   * @param $result - the result of a query call
   * @returns the next row in the result
   */
  public function getRow($result) {
    return sqlite_fetch_array($result);
  }

  /**
   * Frees the result set
   *
   * @param $result - the result set to free
   */
  public function freeResult($result) {
    // no op for sqlite
  }

  /**
   * Gets the number of rows that were affected by the most recent function call.
   *
   * @param $result - the result set to check
   * @returns the number of rows affected
   */
  public function numberOfRowsAffected($result) {
    return sqlite_num_rows($result);
  }
}

?>