javascript - PHP MySQl Chained Select -

i have 2 drop downs populated mysql tables. in mysql tables have foreign key restraints table "assets" has column "department" linked department table. each asset has associated department.

my first dropdown "department" , want second dropdown show results selected department.

here's code.

<select id="location" name="location">     <option value="">select asset location</option>  <?php         $pdo = new pdo('mysql:host=localhost;dbname=maintlog', 'root', '*******');         #set error mode errmode_exception.         $pdo->setattribute( pdo::attr_errmode, pdo::errmode_exception);            $stmt = $pdo->prepare('select id,name location');         $stmt->execute();         while ($row = $stmt->fetch(pdo::fetch_assoc))          {             echo "<option value='$row[id]'>$row[name]</option>";         }   ?> </select>  

and asset:

<select id="asset" name="asset">     <option value="">select asset</option>  <?php         $pdo = new pdo('mysql:host=localhost;dbname=maintlog', 'root', '*****');         #set error mode errmode_exception.         $pdo->setattribute( pdo::attr_errmode, pdo::errmode_exception);            $stmt = $pdo->prepare('select id,assetcode assets');         $stmt->execute();         while ($row = $stmt->fetch(pdo::fetch_assoc))          {             echo "<option value='$row[id]'>$row[assetcode]</option>";         }   ?> </select>  

i have no idea start this, i've done javascript chained selects not mysql/php.

thanks

with mighty parameter binding can reduce ammount of code have write , maintain.

try following example rid of if (1), if (2), if (3) .....

if (filter_input(input_get, "smartload")) {     sleep(1); }  header("access-control-allow-origin: *");  $response[""] = "--";  /* locations , asset  details data  -------------------------------------------------------- */ if (filter_input(input_get, 'location')) {     $pdo = new pdo('mysql:host=localhost;dbname=********', 'root', '********');     #set error mode errmode_exception.     $pdo->setattribute( pdo::attr_errmode, pdo::errmode_exception);        $stmt = $pdo->prepare('select id,assetcode assets location=:getlocation');     $stmt->bindparam(':getlocation', filter_input(input_get, 'location'), pdo::param_int);     $stmt->execute();     while ($row = $stmt->fetch(pdo::fetch_assoc))      {          $response ["$row[id]"]="$row[assetcode]";     } } print json_encode($response); ?> 

bind parameter query , execute. no need repeat code on , over.