How to pass value from <option><select> to form action

Question

I need to pass a value in option select to action where I have agent_id=

Can anyone help?

<form method="POST" action="index.php?action=contact_agent&agent_id=">
<select>
<option value="1">Agent Homer</option>
<option value="2">Agent Lenny</option>
<option value="3">Agent Carl</option>
</select>

Answer 1

You don't have to use jQuery or Javascript.

Use the name tag of the select and let the form do it's job.

<select name="agent_id" id="agent_id">

Answer 2

Like @Shoaib answered, you dont need any jQuery or Javascript. You can to this simply with pure html!

<form method="POST" action="index.php?action=contact_agent">
  <select name="agent_id" required>
    <option value="1">Agent Homer</option>
    <option value="2">Agent Lenny</option>
    <option value="3">Agent Carl</option>
  </select>
  <input type="submit" value="Submit">
</form>

1. Remove &agent_id= from form action since you don't need it there.
2. Add name="agent_id" to the select
3. Optionally add word required do indicate that this selection is required.

Since you are using PHP, then by posting the form to index.php you can catch agent_id with $_POST

/** Since you reference action on `form action` then value of $_GET['action'] will be contact_agent */
$action = $_GET['action'];

/** Value of $_POST['agent_id'] will be selected option value */
$agent_id = $_POST['agent_id']; 

As conclusion for such a simple task you should not use any javascript or jQuery. To @FelipeAlvarez that answers your comment