PHP Editing post - php

Question

I'm having a very annoying problem. Whenever I edit a post, the first time it gets edited, it will lose all of its information. I can't figure it out, I've worked on it for 2 days.
Heres the form code:
<?php
$post = htmlspecialchars($_GET["id"]);
$name = $_SESSION['Username'];
if (in_array($name, $allowedposters)) {
$results = mysql_query("SELECT * FROM tool WHERE id = $post");
while($row = mysql_fetch_array($results)){
$title= $row['title'];
$details= $row['details'];
$date= $row['date'];
$author= $row['author'];
$id= $row['id'];
echo "<a href=story.php?id=";
echo $post;
echo ">Cancel edit</a> <br><br><b>";
echo $title;
echo "</b> <br><br>";
echo '
<form action="edit-new.php?story=';
echo $id;
echo '" method="post" enctype="multipart/form-data">
<textarea rows="1" cols="60" name="title" wrap="physical" maxlength="100">';
echo $title;
echo '</textarea><br>';
?>
<textarea rows="30" cols="60" name="details" wrap="physical" maxlength="10000">
<?php
echo $details;
echo '</textarea><br>';
echo '<label for="file">Upload featured image:</label><br>
<input type="file" name="file" id="file" />';
echo'<br><input type="submit" />';
}
} else {
echo "Not enough permissions.";
}
?>
.
.
Here is the actual php code, inserting information into the database:
.
.
<?php
$post = $_GET['story'];
$title = $_POST['title'];
$details = $_POST['details'];
echo 'Updated.';
$dbtype = "mysql";
$dbhost = "localhost";
$dbname = "x";
$dbuser = "xx";
$dbpass = "xxx";
$conn = new PDO("mysql:host=$dbhost;dbname=$dbname",$dbuser,$dbpass);
$sql = "UPDATE tool SET title=:title, details=:details WHERE id = '$post'";
$q = $conn->prepare($sql);
$q->execute(array(
':details'=>$details,
':title'=>$title,
));
?>
Again, I would like to mention, the only problem is that, the first time I edit the post, it will lose its information. It will never happen to that specific post after that.
The editing works flawlessly, after that.

Answer 1

This doesn't directly answer your question - it would be useful to know what you're actually getting for $_GET['id'], what actual SQL is running on your database and what the generated content of your form looks like.
However:
$post = htmlspecialchars($_GET["id"]);
Is wrong. htmlspecialchars escapes data for output to the client. Encoding special characters for SQL is not going to protect you from SQL injection attacks.
Since $post is expected to be an integer (presumably), this is sufficient:
$post = (int)$_GET['id'];
But be sure to check that a valid integer is returned, and throw an appropriate error if not.
Don't forget to do this again in edit-new.php - even better, use a parametized value like you have done for title and details.
Finally, you should use htmlspecialchars to escape $details and $title in the form. Otherwise content like </textarea> will not be displayed correctly and you are vulnerable to XSS flaws (e.g. followed by <script>alert("I'm going to do bad things now");</script>