class不会返回列表php [关闭]

hi I just started to lear oop and I came acros this problem, whwn I used this script in normal scripring sequence it ecoed out the list of items but when I put it to class file I get only the first line what is the problem? class file:

<?php
class getPVM{
function get ($sql){
     while($row = mysql_fetch_array($sql)){

            $id = $row["product_id"];
            $product_name = $row["product_name"];
            $price = $row["price"];

            return $list =' <li>'.$id .' '.$product_name.' '.$price.'(PVM '.$price*0.21 .') </br></li>';

            }
    }   
}

and I call it like this:

$sql = mysql_query("SELECT * FROM product");
    echo $list=($getPVM->get($sql))

Use the below code and try:

class getPVM{
function get ($sql){
 $list = '';
 while($row = mysql_fetch_array($sql)){

      $id = $row["product_id"];
        $product_name = $row["product_name"];
        $price = $row["price"];

         $list .=' <li>'.$id .' '.$product_name.' '.$price.'(PVM '.$price*0.21 .') </br></li>';

        }

        return $list;
}   
}

You return your value too early and you are not returning your list. Try this:

<?php
class getPVM
{
    function get($sql) 
    {
        $list = "";
        while ($row = mysql_fetch_array($sql)) {
            $product_name = $row["product_name"];
            $price = $row["price"];

            $list .= ' <li>'.$id.' '.$product_name.' '.$price.'(PVM '.$price*0.21.') </br></li>';
        }

        return $list;
    }   
}

To explain this a little bit:

• $list .= the dot-operator appends the string to `$list``
• return $list; has to be at the end to return the complete list after you added every list item in your while-loop

Try this:

<?php
class getPVM{
  function get ($sql){
     $list = "";
     while($row = mysql_fetch_array($sql)){
        $id = $row["product_id"];
        $product_name = $row["product_name"];
        $price = $row["price"];
        $list =' <li>'.$id .' '.$product_name.' '.$price.'(PVM '.$price*0.21 .') </br></li>';
     }
     return $list; //or whatever you return
  }   
}

You're using return inside loop, try this instead:

class getPVM{
    function get ($sql){
        $list = array();
        while($row = mysql_fetch_array($sql)){

            $id = $row["product_id"];
            $product_name = $row["product_name"];
            $price = $row["price"];

            $list[]=' <li>'.$id .' '.$product_name.' '.$price.'(PVM '.$price*0.21 .') </br></li>';

        }
        return $list;
    }
}