Empty rows created by refreshing page - php

Question

I've searched on the Internet to get my answer, but I couldn't find a helpful one. I've got a page called 'post.php' with a form where I can add an image and submit it to the database.
The big problem is when I go to mysite.com/post.php a new empty row is created automatically in the database, which I clearly don't want. I want only to update the database after clicking on the submit button my code:
the part of INSERT:
<?php
// POST.PHP POSTING NEW CONTENT
include 'config.php';
// values from form
$id=$_POST['id'];
$title=$_POST['title'];
$pic=$_POST['pic'];
$youtube=$_POST['youtube'];
$cat=$_POST['cat'];
// insert data to mysql
$sql = "INSERT INTO post(id, title, pic, youtube, cat)VALUES('$id', '$title', '$pic', '$youtube', '$cat')";
$result=mysql_query($sql);
// succes added
if(!$result){
echo "Something went wrong!";
}
else {
echo "Yeah, buddy! Your content is added.";
}
// end of post script ^^
?>
// end of insert
//POST IMAGE PAGE
if(isset($_GET['pic'])) {
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
title: <input name="title" type="text" id="title"><br />
Add url of image;<br />
<input type="text" name="pic" id="pic"/><br />
<?php
echo '
Category game:
<select name="cat"> ';
$query2 = mysql_query("SELECT * FROM `category`");
while($row=mysql_fetch_array($query2)){
echo '
<option value="'.$row["nameID"].'">'.$row["name"].'</option> ';
}
?>
</select>
<input type="submit" onclick="this.disabled = true" name="submit" value="submit">
</form>
<?php
// end script of posting picture
}
?>

Answer 1

You need to add some conditional code around the part that inserts into the database, checking for if any values has been received (if($myvar){ // do stuff }).
Add the rest of your code, specifically the part that adds stuff to the database as that is what's causing you problems, not the code you posted.

Answer 2

You need to wrap the whole block of database insertion code in an if statement. That way, it will not execute until the form has been submitted and $_POST['submit'] has a value:
include 'config.php';
if (isset($_POST['submit'])){
// values from form
$id=$_POST['id'];
// etc... code stays the same down to:
echo "Yeah, buddy! Your content is added.";
}
}//end if (don't forget to add this last bracket)
Also, you should switch to mysqli or PDO, and use parameterized queries. Otherwise, your site is open to a variety of gnarly attacks via SQL injection. It's not that hard to switch, and very, very important.

Answer 3

Check if the post have been set on the file that handles the database input.
if(isset($_POST['pic'])){
//do something
}
else{ // handle the exeption}
Also, you should not use mysql_* functions anymore. they are unsafe and deprecated as-of php 5.5