invalid MySQL argument in mysql_fetch_array

Question

Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in /rideanddrive/_classes/__base.php on line 45

My code :

public static function SelectSpecific($obj, $data_base, $cond)
{
    self::$query = "select $obj from " . self::$baseprefix . "$data_base where $cond";
    $out = self::Execute();
    $array = mysql_fetch_array($out); // THIS LINE IS WARNING LINE
    return $array[$obj];
}

Execute function, if needed :

private static function Execute() 
{
    $out = mysql_query(self::$query);
    return $out;
}

Code's works fine. I don't get a warning on localhost (running WAMP, might have turned them off ?), it also works on live server, however I'm getting the above warning, how do I correct it so the warning is gone ?

Answer 1

On Your SelectSpecific function embed a if check to see your execute function returning proper resource for result .. if not then echo your sql then run it on server separately so that if you can find a error if there is any error with sql ,here is the updated function with if embedded

public static function SelectSpecific($obj, $data_base, $cond)
    {
        self::$query = "select $obj from " . self::$baseprefix . "$data_base where $cond";
        $out = self::Execute();
        if($out){
          $array = mysql_fetch_array($out); // THIS LINE IS WARNING LINE
          return $array[$obj];
       }else {
         return false;
       }
    }

Answer 2

This warning indicates, that there is - for some reason - a (syntactic or semantic) problem with your SQL query, so that mysql_query returns FALSE instead of a MySQL result resource.

You can use mysql_error() to retrieve the error message from MySQL as string for debugging.

---

Please note, that the mysql extension you're using is deprecated as of PHP 5.5 and will be removed in future releases of PHP. Consider switching to mysqli.

Answer 3

Your query probably returns FALSE because of an error.

For SELECT, SHOW, DESCRIBE, EXPLAIN and other statements returning resultset, mysql_query() returns a resource on success, or FALSE on error.

Source

var_dump() your $out to see if it's FALSE.

And even better, just display your error to debug:

if (!$out) {
    $message  = 'Invalid query: ' . mysql_error() . "\n";
    $message .= 'Whole query: ' . $query;
    die($message);
}

BTW, you shouldn't use mysql_query() and all other mysql_* functions anymore as they are deprecated. Use mysqli or PDO instead.