Question

I am trying to extend the PHP5 MySQLi Library

class mysqli_ls extends mysqli

The reason I am extending the class is to add functionality and features I require that are not included by default. For the functions I create I would like to handle errors in exactly the same way as i would any of the native functions..

I would like the person using the class not have to determine if the functions are native or bespoke.

Normal Function

if ( $_mysqli->query($sql) === false ) die($_mysqli->error);

Required Bespoke Function Example

if ( $_mysqli->run_config() === false ) die($_mysqli->error);

Class

Within my class mysqli_ls that is extending mysqli, i have the following functions which i hoped would set the error message within the parent mysqli class..

   public function run_config()
   {
      // Open Debug FH
      if ($this->config['debug_log'] === TRUE)
      {
         if ($this->fh_debug = fopen($this->config['debug_log_path'], 'a') === FALSE) 
         {
            $this->handle_error('Could not open Debug file handle','200',__METHOD__);
            return $this->E_ERROR;
         }
      }
  }



private function handle_error($errormsg,$errorno,$method)
   {
      $this->errorno = $errorno;
      $this->error   = $errormsg;

      if ($this->config['debug_log'] === TRUE)
      {
         $msg = "($errorno) $errormsg";                              
         $this->write_log('error', $method, $msg);
      }

      return $this->E_OK;
   }

I have tried the above method which errors out with:
PHP Fatal error: mysqli_ls::handle_error(): Cannot write property

and the static call syntax which results in a syntax error as seen below:

parent::error
parent::errorno 

I would like the users of the class to have the default MySQLI functionality and the extended functionality seamlessly without having to use different methods to identify errors.

Thanks in advance for any advise or input given..

EDIT: Adding the full class

class mysqli_ls extends mysqli
{
   private $config = array
   (
      'config_load'     => FALSE,
      'config_path'     => 'mysqli_ls.database.ini',

      'debug_log'       => FALSE,
      'debug_log_path'  => '/tmp/mysqli_ls.debug.log',

      'query_log'       => FALSE,
      'query_log_path'  => '/tmp/mysqli_ls.debug.log',

      'log_date_format' => 'Y-m-d H:i:s'
   );

   // Expected fields for the autoload file
   private $db_fields = array('hostname','username','password','database','port');

   // File Handles
   private $fh_debug  = FALSE;
   private $fh_query  = FALSE;
   private $fh_config = FALSE;

   // Return presets
   private $E_OK    = TRUE;
   private $E_ERROR = FALSE;

   // Existing database connections
   private $db_existing = array();

   public $error;
   public $errorno;

   ## ----------
   public function __construct()
   {
      if (!function_exists('mysqli_connect')) $this->handle_error('MySQLI is not installed','100');
   }

   ## ----------
   public function run_config()
   {
      // Testing error handling
      $this->handle_error('Could not open Debug file handle','200',__METHOD__);

      // Open Debug FH
      if ($this->config['debug_log'] === TRUE)
      {
         if ($this->fh_debug = fopen($this->config['debug_log_path'], 'a') === FALSE) 
         {
            $this->handle_error('Could not open Debug file handle','200',__METHOD__);
            return $this->E_ERROR;
         }
      }

      // Open Query FH
      if ($this->config['query_log'] === TRUE) 
      {
         if ($this->fh_query = fopen($this->config['query_log_path'], 'a') === FALSE)
         {
            $this->handle_error('Could not open Debug file handle','210');            
            return $this->E_ERROR;
         }
      }

      // Load database INI file
      if ($this->config['config_load'] === TRUE)
      {
         if ( ($this->db_existing = parse_ini_file($this->config['config_path'], TRUE)) === FALSE )
         {
            $this->handle_error('Could not parse the database ini file','220'); 
            return $this->E_ERROR;
         }
      }

      // Check for format of the loaded ini file
      foreach($this->db_existing as $name => $row)
      {
         foreach($this->db_fields as $field)
         {
            if ( !isset($row[$field]) ) 
            {
               $this->handle_error("Missing field ($field) in the config array for element ($name)",'230'); 
               return $this->E_ERROR;
            }
         } // END foreach
      } // END foreach

      return $this->E_OK;
   }

   ## ----------
   public function set_config($key, $value)
   {
      if ( !isset($this->config[$key]) ) 
      {
         $this->handle_error('Configuration variable ($key) does not exist','300');
         return $this->E_ERROR;
      }

      $this->config[$key] = $value;
      return $this->E_OK;
   }

   ## ----------
   public function get_config()
   {
      return array_merge($this->config, $this->db_existing);
   }

   ## ----------
   private function write_log($type,$method,$msg)
   {
      $msg = date($this->config['log_date_format']) ."\t". $type ."\t". $method ."\t". $msg ."\n";

      switch($type)
      {
         case 'error':
            fwrite($this->fh_debug, $msg);
         break;

         case 'debug':
            fwrite($this->fh_debug, $msg);
         break;

         case 'query':
            fwrite($this->fh_query, $msg);
         break;

         default:
            return $this->E_ERROR;
         break;      
      }
   }

   ## ----------
   private function handle_error($errormsg,$errorno,$method)
   {
      $this->errorno = $errorno;
      $this->error   = $errormsg;

      if ($this->config['debug_log'] === TRUE)
      {
         $msg = "($errorno) $errormsg";                              
         $this->write_log('error', $method, $msg);
      }

      return $this->E_OK;
   }

   ## ----------
   ## ----------
   ## ----------
   ## ----------      

} // END Class

TEST Script Calling the Class

#!/usr/bin/php
<?php

require('mysqli_ls.class.php');

try
{
   $_mysqli = new mysqli_ls;
}
catch (Exception $e)
{
  print "\n\n". $e->getMessage() ."\n\n";
   print_r($e);
}

$_mysqli->set_config('debug_log',TRUE);
$_mysqli->set_config('query_log',TRUE);
$_mysqli->set_config('config_load',TRUE);

$_mysqli->run_config();
print_r($_mysqli->get_config());

?>

EDIT: So it looks like the error variables in the MySQLi class might be readonly..Is there another way around this issue? Im thinking maybe have my own error function that checks the parent class AND my own variables.

Answer 1

Using the __get magic function, you can do something which will check if the parent’s error variable is set. Something like that:

class mysqli_ls extends mysqli{
  public $error;
  public $errorno;
  public $connect_error;
  public $connect_errorno;

  function __get($key){
    if(in_array($key, array('error', 'errorno', 'connect_error', 'connect_errorno'))){
      $parentValue = parent::$key;
      if(empty($parentValue)){
        return $this->$key;
      }
      return $parentValue;
    }
  }
}

Little test script:

<?php
$test = @new mysqli2('localhost', 'badlogin', 'whatisapassword', 'anonexistentdb');
echo 'test : '.$test->connect_error;