php - Show/hide select values based on previous select choice -

i have 2 select's inside form. second select has 2000 lines in total coming out of mysql table. 1 of column mysql has 1 of values used first select. want able filter on value when selected first select, shows these articles.

code now:

<div class="rmaform">    <select name="discipline" class="discipline">       <option value="&nbsp;" selected></option>       <option value="access">access</option>       <option value="inbraak">inbraak</option>       <option value="brand">brand</option>       <option value="cctv">cctv</option>       <option value="airphone">airphone</option>       <option value="perimeter">perimeter</option>    </select> </div>              <div class="rmaform"> <select name="article" class="input-article">    <?php       $articleselect = $dbh->prepare('select * articles');       $articleselect->execute();          while($articlerow = $articleselect->fetch(pdo::fetch_assoc)){    ?>       <option value="<?php echo $articlerow['a_code'];?>"><?php echo $articlerow['a_code'];?> <?php echo $articlerow['a_omschr_nl'];?></option>    <?php       }    ?> </select> 

i think have use javascript how combine php , javascript? , best way make filter work?

jquery change event , ajax

$(document).ready(function(e) {     $('select.discipline').change(function(e) { // when select changed         var sel_value=$(this).val(); // chosen value         $.ajax(         {             type: "post",             url: "ajax.php", // new php page option value, process , return possible options second select             data: {selected_option: sel_value}, // send slected option php page             datatype:"html",             success: function(data)             {                 $('select.input-article').append(data); // append possible values second select             }         });     }); }); 

in ajax.php

<?php if(isset($_post['selected_option']))     $selected_option=filter_input(input_post, "selected_option", filter_sanitize_string); else exit(); // no value sent  $query="select * articles discipline='$selected_option'"; // example. build query per logic  // process query  $options=""; while($query->fetch()) // simplicity. proceed pdo {     $options.="<option value='option_value'>text option</option>"; // option_value value option , text option text displayed particular option } echo $options; ?> 

note: can use json instead of html simplicity. read here, how to.