if specific select option is chosen get the value of input - php

Question

I have a little knowledge of php, but this is what I'm trying to do. I have a form with select option. If an option is selected with the value "example_5" I want it to get the value of an <input>. Is this done with php or jquery to use the value of input?
For example: someone selects example_5. They can now write something in the <input>. And that value will be used.
<script type="text/javascript">
$(function(){
if($('select').find('option:selected').val() == 'example_5'){
use input??
$_COOKIE['input_example'] = $example_1;
}
else{
$_COOKIE['example_1'] = $example_1;
}
});
</script>
<?php
$_COOKIE['example_1'] = $example_1;
?>
<form method="get" action="page2.php">
<select name="example1">
<option value="example_1">example_1</option>
<option value="example_2">example_2</option>
<option value="example_3">example_3</option>
<option value="example_4">example_4</option>
<option value="example_5">example_5</option>
</select>
<input name="input_example" type="text">
</form>

Answer 1

The way I would do it is to have a onChange listener on the select box and then using javascript get the value of the input box using document.getElementById. You can use any jQuery shortcut you want, but the methodology would be the same.
See this fiddle for a functional example using this technique.
On an unrelated note, be sure to always close your <input /> tags (probably just a typos :)
Edit
As per comment : just set the value of the input from a value from the cookies.
document.getElementById("input_example").value = getCookie("cookie_name");
Where you can write a simple function to get the cookies :
function getCookie(Name) {
var search = Name + “=”
if (document.cookie.length > 0) { // if there are any cookies
offset = document.cookie.indexOf(search)
if (offset != -1) { // if cookie exists
offset += search.length
// set index of beginning of value
end = document.cookie.indexOf(”;”, offset)
// set index of end of cookie value
if (end == -1)
end = document.cookie.length
return unescape(document.cookie.substring(offset, end))
}
}
}
Tutorial for js cookie function taken here.
See also
JS Cookies

Answer 2

Based on your comment to blo0p3r's answer.
In page2.php, add the following at the very top of the script before any whitespace or HTML is sent:
<?php
if (isset($_GET['example1']) && $_GET['example1'] === "example_5")
setcookie($_GET['input_example'], 'example_5', time()+3600, '/');

Answer 3

First, you want to check if the from is submitted. Afterward $_COOKIE['example_1'] = $example_1; would be something like this:
$_COOKIE['example_1'] = $_GET['example1'];