jquery autocomplete sql query list based on another input value - php

Question

I have two autocomplete fields in my form. I populate the first field's list by using the following code...
$result = mysql_query("SELECT * FROM exercise_strength");
$arr_autoCompleteExerciseStr=array();
$s=0;
while($row = mysql_fetch_array($result)){
$autoCompleteExerciseStr = "\"".ucfirst($row['exercise'])."\", ";
$arr_autoCompleteExerciseStr[$s] = $autoCompleteExerciseStr;
$s++;
}
and...
$(function() {
var availableTags = [
<?php for($k=0; $k<sizeof($arr_autoCompleteExerciseStr); $k++) {echo $arr_autoCompleteExerciseStr[$k]; } ?>
];
$( "#inputExercise" ).autocomplete({
source: availableTags,
minLength: 0
});
$( "#inputExercise" ).focus(function(){
$(this).autocomplete("search");
});
});
The same code with a different mysql_query is used for the other field. What I want to do is change the list of the second field based on what's typed in the first. For instance, if the user types Chest in the first field, a list of relevant Exercises is shown in the second field, selected from my sql database.
What is the best way to do this?
I would prefer if I wouldn't have to leave the page, cause then the user have to refill the rest of the form..
Please help! :)
-- UPDATE --
Based on your advice about JSON my code now looks like this.
Script:
$(document).ready(function(){
$.post('json_exercise.php', { /**/ }, showExercise, "text");
});
function showExercise(res){
var list = JSON.parse(res);
$("#inputExercise").autocomplete({
source: list,
minLength: 0
});
$( "#inputExercise" ).focus(function(){
$(this).autocomplete("search");
});
}
PHP file:
$con = mysql_connect(***);
if (!$con) {die('Could not connect: ' . mysql_error());}
mysql_select_db("test", $con);
$result = mysql_query("SELECT * FROM exercise_strength");
$i = 0;
while($row = mysql_fetch_array($result, MYSQL_ASSOC))
{
//add the row to the $chat array at specific index of $i
$exercise[$i] = $row['exercise'];
$i += 1;
}
echo json_encode($exercise);
Now I just need to change the php filed based on whats selected in the first autocomplete field.

Answer 1

If you want to autocomplete based on results from a SQL query without having to leave the page, you might want to look into AJAX and JSON.
Also, please use PDO instead of the mysql_* functions for interfacing with DBMS's with PHP.