Correct php syntax - php

Question

// query
$sql = "INSERT INTO tool (title,details) VALUES (:title,:details) ";
$q = $conn->prepare($sql);
$q->execute(array(':details'=>$details,
':title'=>$title));
Been having trouble with this all day, I've finally got it down to this. If I use the above code, it will just add a new post to the database. This is supposed to be used for editing a post, so obviously I need to edit existing information:
// query
$post = htmlspecialchars($_GET['story']);
$sql = "UPDATE tool SET (title,details) VALUES (:title,:details) WHERE id = $post";
$q = $conn->prepare($sql);
$q->execute(array(':details'=>$details,
':title'=>$title));
'id' is a column in the database. I need it to update the title, and details, for that specific post. I'm just not sure what syntax I'm supposed to be using here.
Thanks for any answers!
===== Second question:
Now I'm back to my old error. Whenever I edit a post, it will lose the title and details, only once. The first time I edit the post, I lose all information, but the rest of the times it will work just fine. Any idea why? Heres the code:
Form from the edit page(may or may not be important, I don't know):
$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 SQL, inserting into DB:
<?php
$post = htmlspecialchars($_GET['story']);
$title = mysql_real_escape_string($_POST['title']);
$details = mysql_real_escape_string($_POST['details']);
echo "B<br>";
echo $_POST['title'];
echo '<br>';
echo $_POST['details'];
echo $post;
echo "<br><br>";
// configuration
$dbtype = "mysql";
$dbhost = "localhost";
$dbname = "zzzz";
$dbuser = "zzzzz";
$dbpass = "zzzzzz";
// database connection
$conn = new PDO("mysql:host=$dbhost;dbname=$dbname",$dbuser,$dbpass);
// new data
// query
$sql = "UPDATE tool SET title=:title, details=:details WHERE id = :postid";
$q = $conn->prepare($sql);
$q->execute(array(
':details'=>$details,
':title'=>$title,
':postid' => $post
));
?>

Answer 1

Fix your sql UPDATE syntax
$sql = "UPDATE tool SET title=:title, details=:details WHERE id = :postid";
$q = $conn->prepare($sql);
$q->execute(array(
':details'=>$details,
':title'=>$title,
':postid' => $post
));