I have seen a few posts similar to my question, but was unable to successfully integrate it into my scenario. I anticipate that this is a short, easy fix (for someone with experience) but I'm not embarrassed to say that I'm a total newb.
Ok, so, I have a successful contact form with jquery validation on it. I am just looking to add a "File Upload" to the form, for people to attach their resumes. I was able to add the HTML portion for the file upload field/button, but need some help with integrating the PHP side... if anyone is in a position to help me, I would be very grateful (especially since I'm working on Christmas Day!

).
My form is as follows (I'll leave out the jquery validation portion, along with the CSS, for simplicity):
HTML Code:
<form id="form_id" class="AdvancedForm" action="application_form_submission.php" method="post" onsubmit="javascript
:return validate('form_id','email');">
<table cellpadding="3" cellspacing="2">
<tr>
<td>
First Name:
</td>
<td>
<input type="text" name="firstname" id="firstname" />
</td>
</tr>
<tr>
<td>
Last Name:
</td>
<td>
<input type="text" name="lastname" id="lastname" />
</td>
</tr>
<tr>
<td>
Primary Phone #:
</td>
<td>
<input type="text" name="mainphone" id="mainphone" />
</td>
</tr>
<tr>
<td>
Alternate Phone #:
</td>
<td>
<input type="text" name="secondphone" id="secondphone" />
</td>
</tr>
<tr>
<td>
Enter Email ID:
</td>
<td>
<input type="text" name="email" id="email" />
</td>
</tr>
<tr>
<td>
Preferred Contact Method:
</td>
<td>
<select name="preferred_contact" id="preferred_contact">
<option value="mainphone" selected="selected">Main Phone</option>
<option value="secondaryphone">Secondary Phone</option>
<option value="Email">Email</option>
</select>
</td>
</tr>
<tr>
<td>
Preferred Contact Time:<br />(if via phone)
</td>
<td>
<select name="preferred_contact_time" id="preferred_contact_time">
<option value="not_specified">Please select...</option>
<option value="morning">Morning</option>
<option value="afternoon">Afternoon</option>
<option value="evening">Evening</option>
</select>
</td>
</tr>
<tr>
<td>
Are you willing to relocate?
</td>
<td>
<span id="relocate" class="InputGroup">
<label for="relocate_1">
<input type="checkbox" name="relocate1" id="relocate1" value="yes" />Yes
</label>
<label for="relocate_2" style="padding-left: 10px;">
<input type="checkbox" name="relocate2" id="relocate2" value="no" />No
</label>
</span>
</td>
</tr>
<tr>
<td>
Please attach your resume:
</td>
<td><input name="upload_1" tabindex="9" type="file" onchange="attachmentChanged()" size="25" /></td>
</tr>
<tr>
<td>
</td>
<td>
<input class="button" type="submit" value="Submit" name="submit"/>
</td>
</tr>
</table>
PHP File (i.e. "application_form_submission.php):
<SCRIPT LANGUAGE="javascript">
self.location="form_submit.html"
</SCRIPT>
<?php
if(isset($_POST['submit'])) {
$to = "testing@hotmail.com";
$subject = "New Employment Application";
$firstname = $_POST['firstname'];
$lastname = $_POST['lastname'];
$mainphone = $_POST['mainphone'];
$secondphone = $_POST['secondphone'];
$email = $_POST['email'];
$preferred_contact = $_POST['preferred_contact'];
$preferred_contact_time = $_POST['preferred_contact_time'];
$relocate1 = $_POST ['relocate1'];
$relocate2 = $_POST['relocate2'];
$body = "
$firstname $lastname has sent in an application for employment. Details are as follows: \n \n
From: $firstname $lastname\n
Main Phone: $mainphone\n
Alternate Phone: $secondphone\n
Email: $email\n
Preferred Contact Method: $preferred_contact\n
Preferred Contact Time: $preferred_contact_time\n
Relocate: $relocate1 $relocate2\n
\n";
echo "Use Browser Back Button to return";
mail($to, $subject, $body);
} else {
echo "Please fill out all information!";
}
?>
----------------------------
Thanks in advance for any help provided!!