Disable select option when other specifig value is selected - php

Question

I have a question by these given information:
private function loadIntervallOptions($intervallid = 1, $intervallfactor=1){
echo "<select name='intervallfactor'>";
for($intervallnumber=1;$intervallnumber<10;$intervallnumber++){
$checked = "";
if($intervallnumber== $intervallfactor){
$checked = "selected";
}
echo "<option $checked>$intervallnumber</option>";
}
echo "</select>";
echo "<select name='intervallid'>";
for($i=0;$i<count($this->todo_intervall);$i++){
echo "<option value='{$this->todo_intervall[$i]->getintervallid()}' ";
if($this->todo_intervall[$i]->getIntervallid() == $intervallid){
echo "selected";
}
echo ">{$this->todo_intervall[$i]->getIntervall()}</option>";
}
echo "</select>";
}
What I want to do:
If intervallid=1 I want to hide the select 'intervallfactor'. Is this possible?
Thank you in advance!
EDIT:
I'm trying this but it won't work
$('.intervallid').change(function(e) {
if ($('.intervallid').val()==1){
$('.intervallfactor').attr('disabled','disabled');
}
else{
$('.intervallfactor').removeAttr('disabled');
}
});
$('.intervallid').trigger('change');

Answer 1

You are trying to reference the html element using a class name .intervallid which doesnt exist.
either you should use $('select[name="intervalid"]) or add an id to the select from php and, use that to reference the element.
PHP
echo "<select name='intervallid' id='intervall_id'>";
JS
$('#intervall_id').attr('disabled', 'true')