PHP的MySQL查询致命错误

Question

i have this php code to fill a table with some data come to an mysl db, but when i exec it said

"Fatal error: Call to undefined method MysqlClass::query()"


<?php 
include "config.php"; 
$data = new Mysqlclass();
$data->connetti(); 
$post_sql = $data->query("SELECT * FROM products ORDER BY id DESC"); 
if(mysql_num_rows($post_sql) > 0) 
    {while($post_obj = $Data->estrai($post_sql))
        {$id=$post_obj->id; 
            $name = stripcslashes($post_obj->name); 
            $cat = stripcslashes($post_obj->category);
            $price= stripcslashes($post_obj->price);
            echo "<td>".$id."</td>";
            echo "<td>".$name."</td>";
            echo "<td>".$cat."</td>";
            echo "<td>".$price."</td>";
        }
    }else{
        echo"Tabella vuota";
    }
    $data->disconnetti();
?>

The error is in 2 line when i declare the $Data->query .

maybe the function query is not correct, i'm new to php scripting.

I've taken this code in a tutorial. i don't know if the "query" and "estrai" (extract) key is correct.

Here is the config file:

<?php

    class MysqlClass
    {
      private $nomehost = "localhost";     
      private $nomeuser = "root";          
      private $password = "xxxxx"; 
      private $nomedb = "intse";
      private $attiva = false;
      public function connetti()
      {
        if(!$this->attiva)
        {
          if($connessione = mysql_connect($this->nomehost,$this->nomeuser,$this->password) or die (mysql_error()))
          {
            $selezione = mysql_select_db($this->nomedb,$connessione) or die (mysql_error());
          }
        } else{
          return true;
        }
      } 
      public function disconnetti()
      {
        if($this->attiva)
        {
          if(mysql_close())
          {
            $this->attiva = false; 
            return true; 
          } else {
             return false; 
          }
        }
      }
    }  
    ?>

http://imageshack.com/a/img35/1966/pd0v.png So now i must to fill row2 with db 2nd entry and row3 with db 3rd entry, and increase number of table row in html to fill other db entries. thanks.

Answer 1

Variables are case sensitive, ($Data->estrai);
Using $data->query will use the query method from your MysqlClass class, not the system predefined one, you you need to write one for it. If you want to use the method from your class like $data->method(), you need to build it in your class. For example

public function query($sql) {

    return mysql_query($sql);

}

Also I can't see the usage of $this->attiva since you didn't set it to TRUE somewhere. $selezione is also useless.

UPDATES:

mysql_select_db only returns a boolean value, you don't need it other than reporting a fail select (die).
It should be something like this (if I didn't make any syntax mistake..):

<?php 

include 'config.php'; 

$data = new MysqlClass();
$data->connetti();

$post_sql = $data->query("SELECT * FROM products ORDER BY id DESC"); 

if(mysql_num_rows($post_sql) > 0) {

    while($post_obj = $data->estrai($post_sql)) {

        // the data it returns is an array, not object
        // so it should be $post_obj['key'] not $post_obj->key

        $id = $post_obj['id'];
        $name = stripcslashes($post_obj['name']);
        $cat = stripcslashes($post_obj['category']);
        $price = stripcslashes($post_obj['price']);

        echo "<td>".$id."</td>";
        echo "<td>".$name."</td>";
        echo "<td>".$cat."</td>";
        echo "<td>".$price."</td>";
    }

} else {

    echo 'Tabella vuota';

}

$data->disconnetti();

?>

.

<?php

class MysqlClass {

    private $nomehost = 'localhost';     
    private $nomeuser = 'root';          
    private $password = 'xxxxx'; 
    private $nomedb = 'intse';
    private $attiva = FALSE;
    private $connessione;

    public function connetti() {

        if(!$this->attiva && ($this->connessione = mysql_connect($this->nomehost, $this->nomeuser, $this->password) or die(mysql_error()))) {

            mysql_select_db($this->nomedb, $this->connessione) or die(mysql_error());
            $this->attiva = TRUE; // Now this becomes useful, because the value has been set

        }

        return $this->attiva;

    } 

    // Method to build up the query

    public function query($sql) {

        return mysql_query($sql, $this->connessione);

    }

    // Method to extract information from the query

    public function estrai($query) {

        return mysql_fetch_array($query, MYSQL_ASSOC);

    }

    public function disconnetti() {

        // More straight forward way to return the status

        if($this->attiva) return mysql_close($this->connessione);

        return FALSE;

    }

}

UPDATE2:

<?php 

include 'config.php'; 

$data = new MysqlClass();
$data->connetti();

$post_sql = $data->query("SELECT * FROM products ORDER BY id DESC"); 

echo '<table>';

if(mysql_num_rows($post_sql) > 0) {

    while($post_obj = $data->estrai($post_sql)) {

        // the data it returns is an array, not object
        // so it should be $post_obj['key'] not $post_obj->key

        $id = $post_obj['id'];
        $name = stripcslashes($post_obj['name']);
        $cat = stripcslashes($post_obj['category']);
        $price = stripcslashes($post_obj['price']);

        echo '<tr>';

        echo "<td>".$id."</td>";
        echo "<td>".$name."</td>";
        echo "<td>".$cat."</td>";
        echo "<td>".$price."</td>";

        echo '</tr>';

    }

} else {

    echo 'Tabella vuota';

}

echo '</table>';

$data->disconnetti();

?>

Answer 2

In the specific line you have an error:

$post_sql = $data->query("SELECT * FROM products ORDER BY id DESC"); 

Change to this:

$post_sql = $Data->query("SELECT * FROM products ORDER BY id DESC"); 

The variable $Data needs to be Uppercase all time (because you created it like that), PHP is a Case sensitive language.

Hope it helps.