PHP: If value is empty, to not sumbit target filepath to database - forms

Question

I have a very slight problem where I am not able to figure out how to get my target filepath not submit to the mysql database when the field value is empty. Right now, if I leave the image field empty, it still submits the filepath ($folder) to the database. I would like for when the field is left empty, to not send the filepath to mysql.
Form.php
<form enctype="multipart/form-data" action="add.php" method="POST">
HAZARD: <input name="haz1" value="hazard1" type="text" /><br>
<input type="hidden" name="MAX_FILE_SIZE" value="10000000" />
IMAGE: <input type="file" name="photo"><br>
<input type="submit" name="action" value="Load">
</form>
Add.php
<?php
$folder = "images/";
$target1 = $folder . basename( $_FILES['photo']['name']);
$photo = $target1;
require("../db.php");
$haz1 = $_POST['haz1'];
mysql_query("INSERT INTO testimg VALUES (null,'$haz1','$photo')") ;
move_uploaded_file($_FILES['photo']['tmp_name'], $target1);
?>
I've tried
if (isset($_POST['photo']) ? $_POST['photo'] : null) echo $target1 == null);
I've tried other ways of isset as well but doesn't seem to work. Is there any other way i can accomplish this? Appreciate any help please. Thank you!
(Just a note, I have removed excess code above just to keep it short. I am taking care of SQL injection)

Answer 1

I would strongly suggest JavaScript, then users do not need to reload the page if it is empty. The JavaScript will check if it is empty for you. If it is you can make it so they cannot submit at all.
function validateForm()
{
var x=document.forms["myForm"]["fname"].value;
if (x==null || x=="")
{
alert("First name must be filled out");
return false;
}
}
This is an example above, if you would like better walk through go here
JQuery has libraries that you can use to do fancy things if it is left blank, just search for JQuery form validation for more tools.
Hope this helps!

Answer 2

Try using the inbuild HTTP_POST_FILE in PHP:
if (isset($_FILES['photo']) ? $_FILES['photo'] : null)
You could wrap the mysql code inside of an if function too:
if (isset($_FILES['photo']) {
//Do mySQL processing in here
}

Answer 3

A couple of points:
Require is at the top of a PHP script. It's nicer to see all requires
first.
I have used an inline if statement to determine what to set $photo
(elimintating need for $target1)
I have also moved the apostrophes into the assignment of $photo as
returning 'null' comapred to null (without the quotation marks) is
very different in SQL.
If $photo is not null at the end of the script then it moves the
updated file.
Please see the corrected code below:
<?php
require("../db.php");
$folder = "images/";
$photo = (isset($_FILES['photo']) ? "'" . $folder . basename( $_FILES['photo']['name']) . "'" : null);
$haz1 = $_POST['haz1'];
mysql_query("INSERT INTO testimg VALUES (null,'$haz1',$photo)") ;
if ($photo != null) { move_uploaded_file($_FILES['photo']['tmp_name'], $photo); }
?>