take a value from a select option and use it on php - php

Question

I have this select , i wanna save each value after change , save it and use in other select
This is my code :
<?
$sql = "SELECT * FROM championnat ";
$result = $conn->query(sprintf($sql));
if($result){
if ($result->num_rows != 0)
{
$rows=array();
?>
<select name="nom_championnat" id="nom_championnat" >
<option value=""></option>
<?php
while($r=mysqli_fetch_assoc($result))
{
?>
<option value=" <?php echo $r['idChampionnat']?>" name="nom_championnat" selected >
<?php echo $r['nomChampionnat'] ?></option>
<?php
}
}
}
?>
</select>
</div>
I need the variable $r['idChampionnat'] to save it in each select and use it in this requete , how can it asve and put it in that requete sql ????
<?php
$sql = "SELECT * FROM equipe where idChampionnat=???? ";
$result = $conn->query(sprintf($sql));
if($result){
if ($result->num_rows != 0)
{
$rows=array();
?>
<select name="equipe1" >
<option value=""></option>
<?php
while($r=mysqli_fetch_assoc($result))
{
?>
<option required value=" <?php echo $r['nomEquipe']?>" name="equipe1" selected ><?php echo $r['nomEquipe'] ?>
</option>
<?php
}
}
}
?>
</select>
just to clear it ,

Answer 1

You need to use jQuery to fire an AJAX call when the first box is selected.
Its been a while since I've done this but this should give you some idea. I took some code from here and here as example
Say your html looks like this
<select id="nom_championnat">
<option value="value1">value1</option>
<option value="value2">value2</option>
</select>
<select id="equipe1"></select>
then you need to tell jquery what to do when nom_championnat changes selection
$('#nom_championnat').change(function() {
var data = "";
$.ajax({
type:"POST",
url : "queryfile.php",
data : "value="+$(this).val(),
async: false,
success : function(response) {
data = response;
return response;
},
error: function() {
alert('Error occured');
}
});
var string = data.message.split(",");
var array = string.filter(function(e){return e;});
var select = $('equipe1');
select.empty();
$.each(array, function(index, value) {
select.append(
$('<option></option>').val(value).html(value)
);
});
});
and then you need a queryfile.php to handle the ajax requests, something like
<?php
print_r($_POST);
$value = $_POST["value"];
$sql = "select where {$value} ..."
$result = execute($sql);
echo $result;
?>