Upload is reading PHP variable as null

I am having trouble getting a picture to load from mysql database. The directory is randomly generated and gets stored in the database just fine. When the page refreshes the img returns a broken link, echos 'not set.', and inspect element tells me that $default_pic isn't defined. I can't figure out what is going on here can anyone help?

<?php
error_reporting(E_ALL); ini_set('display_errors', 1);
$listingid = $_SESSION['edit_listing'];
if(isset($_FILES['listingpic'])){
    if($_FILES['listingpic']['type']=="image/jpeg"||$_FILES['listingpic']['type']=="image/png"||$_FILES['listingpic']['type']=="image/gif"){
        if($_FILES['listingpic']['size']<1048576){
            $chars = "abcdefghijklmanopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
            $rand_dir_name = substr (str_shuffle($chars), 0, 15);
                                    mkdir("userdata/listingpics/$rand_dir_name/") or die("directory error");
            if(file_exists("userdata/listingpics/$rand_dir_name/".$_FILES['listingpic']['name'])){
                echo "File already exists.";
            }
            else{
                move_uploaded_file($_FILES['listingpic']['tmp_name'], "userdata/listingpics/$rand_dir_name/".$_FILES['listingpic']['name']) or die("Failed to move file.");
                $listing_pic_name = $_FILES['listingpic']['name'];
                $listing_pic_query = mysql_query("UPDATE properties SET default_pic='$rand_dir_name/$listing_pic_name' WHERE id='$listingid'"); 
                $default_pic = "userdata/listingpics/$rand_dir_name/".$_FILES['listingpic']['name'];//<-PROBLEM
                header("Location: ../list_property/upload.php?id=".$listingid);
            }
        } else echo "File must not exceed 1MB.";
    } else echo "File must be a JPEG, PNG, or GIF image.";
} else echo "Not set.";

?>
<form action="" method="POST" enctype="multipart/form-data">
    <img src="<?php echo $default_pic; ?>" width="50%" height="50%"/><br>
    <br>
    <input type="file" name="listingpic" />
    <input type="submit" name="uploadpic" value="Upload Picture">
</form>