php form several select with same name only the one selected - php

Question

I have a form with several <select> that have the same name and an onChange="document.forms['form_mes_reservations'].submit();" on all of them. Therefore, when I select an option from one of them, the page reloads and there is some PHP treatment done.
This is an example :
<form method="post" id="form_process">
<select name="processed" onChange="document.forms['form_process'].submit();">
<option value="1_choose">Please choose...</option>
<option value="1_yes">Yes</option>
<option value="1_no"></option>
</select>
<select name="processed" onChange="document.forms['form_process'].submit();">
<option value="2_choose">Please choose...</option>
<option value="2_yes">Yes</option>
<option value="2_no"></option>
</select>
<select name="processed" onChange="document.forms['form_process'].submit();">
<option value="3_choose">Please choose...</option>
<option value="3_yes">Yes</option>
<option value="3_no"></option>
</select>
<select name="processed" onChange="document.forms['form_process'].submit();">
<option value="4_choose">Please choose...</option>
<option value="4_yes">Yes</option>
<option value="4_no"></option>
</select>
</form>
What I'd like to know is this : is there a way to know which select has triggered the onChange ? Let me explain : in the $_POST['processed'], I get ALL the selected options, so if I have only selected "3_yes", I'll get something like this :
1_choose
2_choose
3_yes
4_choose
Is it possible to only have "3_yes" as a result ? Potentially, this is going to be a very long list of selects and I don't want to check all of them for changes...

Answer 1

Just make all select elements as array and check which is selected:
HTML:
<form method="post" id="form_process" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<select name="processed[]" onChange="document.forms['form_process'].submit();">
<option value="1_choose">Please choose...</option>
<option value="1_yes">Yes</option>
<option value="1_no"></option>
</select>
<select name="processed[]" onChange="document.forms['form_process'].submit();">
<option value="2_choose">Please choose...</option>
<option value="2_yes">Yes</option>
<option value="2_no"></option>
</select>
<select name="processed[]" onChange="document.forms['form_process'].submit();">
<option value="3_choose">Please choose...</option>
<option value="3_yes">Yes</option>
<option value="3_no"></option>
</select>
<select name="processed[]" onChange="document.forms['form_process'].submit();">
<option value="4_choose">Please choose...</option>
<option value="4_yes">Yes</option>
<option value="4_no"></option>
</select>
</form>
PHP:
<?php
foreach($_POST['processed'] AS $key => $value){
if(strpos($value, 'choose') !== false){
unset($_POST[processed][$key]);
}
}
print_r($_POST['processed']);
?>
Output:
Array
(
[1] => 2_yes
)