Upload image with caption and store caption & session username to database - php

Question

I want to implement a simple image uploader that stores a caption, the user logged in ($_SESSION['username']) and the path that the file is saved.
The session is working, the code is correct, the database table exists, but it writes only the 'path' value, the 'username' and 'caption' remain empty on the database.
This is the code for uploading:
if ((($_FILES["file"]["type"] == "image/gif")
|| ($_FILES["file"]["type"] == "image/jpeg")
|| ($_FILES["file"]["type"] == "image/jpg")
|| ($_FILES["file"]["type"] == "image/pjpeg")
|| ($_FILES["file"]["type"] == "image/x-png")
|| ($_FILES["file"]["type"] == "image/png"))
&& ($_FILES["file"]["size"] < 5000000)
&& in_array($extension, $allowedExts)) {
if ($_FILES["file"]["error"] > 0) {
echo "Return Code: " . $_FILES["file"]["error"] . "<br>";
} else {
if (file_exists("upload/" . $_FILES["file"]["name"])) {
echo $_FILES["file"]["name"] . " already exists. ";
} else {
move_uploaded_file($_FILES["file"]["tmp_name"],
"upload/" . $_FILES["file"]["name"]);
$caption = $_POST['caption'];
$uploaderUsername = $_SESSION['username'];
$path = "upload/" . $_FILES['file']['name'];
mysql_connect("localhost","root","") or die(mysql_error());
mysql_select_db("mydb") or die(mysql_error());
mysql_query("INSERT INTO images (caption,username,path) VALUES
('$caption','$uploaderUsername','$path')");
header('Location: members.php');
}
}
} else {
echo "Invalid file";
}
I guess there is something wrong in this part:
$caption = $_POST['caption'];
$uploaderUsername = $_SESSION['username'];
$path = "upload/" . $_FILES['file']['name'];
mysql_connect("localhost","root","") or die(mysql_error());
mysql_select_db("mydb") or die(mysql_error());
mysql_query("INSERT INTO images (caption,username,path) VALUES
('$caption','$uploaderUsername','$path')");
header('Location: members.php');

Answer 1

To add to my note above
"I don't see you calling session_start() before attempting to access the session variables. (which just happen to be one of the two variables you aren't getting :O). And in your form make sure you are setting the name='caption' for the caption input"
using the code you provided, to implement the caption you would want to do something along the lines of
<form action="upload_file.php" method="post" enctype="multipart/form-data">
<label for="file">Filename:</label>
<input type="file" name="file" id="file"><br>
<label for="caption">Caption: </label>
<input type="text" id="caption" name="caption" placeholder="Add a caption here"><br>
<input type="submit" name="submit" value="Submit">
</form>