mysql的下拉列表的值

Question

I'm trying to compose an estimate formula, and I stucked with value of dropdown list populated by MySQL.

The idea of this formula is when a user select a service from dropdown list and put the quantity in textfield the program will compute the price for the service.

The value of the prize is selected from MySQL table.

$query="SELECT $con_tent FROM services WHERE $id;
$con_tent= 'price'. '*'. $qunatity

But I don't know how to get the value from dropdwon list.

Probably with Ajax but still don't know how.

I solved this by modyfing code from http://www.9lessons.info/2010/08/dynamic-dependent-select-box-using.html

<?php
    require_once 'login.php';
    $db_server = mysql_connect($db_hostname, $db_user, $db_password);
    mysql_select_db($db_database) or die("unable to select database:" . mysql_error());

    echo "<form action=licz.php method='post'>";
    echo " <label for=\"select\"><select name=\"\" value=\"Select\" size=\"1\">";

    $query = "SELECT * FROM uslugi ORDER BY id ASC";
    $result = mysql_query($query);
    while ($row = mysql_fetch_array($result)) {
        global $ff;

        $ajdi = $row['id'];

        $nazwa = $row['nazwa'];
        $options.= "<option value=\"$ajdi\" name=\"oko\">" . $nazwa . $ajdi;
    }
    echo "<option>";
    echo $options;

    echo "</option></select>";
    echo "  <input type=\"submit\" name=\"Submit\" value=\"Submit\">";

    echo "</form>";
    function wybor() {
        global $id;
        global $con_tent;
        $var = 'price' . '*';
        $quantity = 3;
         //quantity will by from textfield but now it constant
        $id_value = 1;
         // here i need to make it dynamic
        $id = "id={$id_value}";
        $con_tent = $var . $quantity;
    }

    echo wybor();

    $query = "SELECT $con_tent FROM services WHERE $id";
     //query

    if (!$query) Die("Unable to query: " . mysql_error());

    $result = mysql_query($query);

    if (!$result) Die("Unable to query: " . mysql_error());
    $rows = mysql_num_rows($result);
    for ($a = 0; $a < $rows; ++$a) {
        $row = mysql_fetch_row($result);

        echo $row[0] . " ";
        echo $row[1] . " ";
        echo $row[2] . " ";
        echo $row[3] . "$br";
    }


?>

Answer 1

You should apply ajax call to get value for database when there is a change in select box through calling a function on onchange event of javascript.

Read More for jquery AJAX

http://www.sitepoint.com/ajax-jquery/

http://www.tutorialspoint.com/jquery/jquery-ajax.htm