Dynamic CMS problem

[dev2012]

I am using PHP and MySQL to build a dynamic CMS. I am really new to this. I set up my SQL database with the following
web_pages
id page_title url content

These files have the following codes:

//header.php
<?php
//Variables for the database

$host = 'localhost';
$username = '###########';
$password = '######';
$dbname = '###########';
?>

//nav.php
$conn = mysqli_connect($host, $username, $password, $dbname) or die('Error connecting to MySQL server.');

$sql = "SELECT id, page_title, url FROM web_pages;";
$result = mysqli_query($conn, $sql) or die('Error querying database.');

//loop through the page titles to populate the navigation bar
while ($row = mysqli_fetch_array($result)) {
$page_title = $row['page_title'];
$url = $row['url'];
echo "<ul><li><a href=' " . $row['id'] . " '> " . $row['page_title'] . "</a></li></ul>";
}

mysqli_close($conn);

?>


//default.php
<header>
<?php
require_once("header.php");
require_once("nav.php");
?>
</header>

<!-- +++++++++++++++++++++++ CONTENT +++++++++++++++++++++ -->

<div id="content">
<?php
$conn = mysqli_connect($host, $username, $password, $dbname) or die('Error connecting to MySQL server.');

$sql = "SELECT page_title, url, content FROM web_pages WHERE content = '$content';";
$result = mysqli_query($conn, $sql) or die('Error querying database.');

while ($row = mysqli_fetch_array($result)) {
$id = $row['id'];
$page_title = $row['page_title'];
$url = $_GET['url'];
$content = $row['content'];
}

if(!isset($_GET['id'])) {

echo $row['content'];
}
else
echo "default.php";
mysqli_close($conn);
?>

</div>

Rather than the user click on the navigation and it directing to a new non-existant page I want the content from the database to show up in the content section of the default page.

PLEASE HELP!! I need to get this working by tonight!

[SambaNeko]

In this query:

$sql = "SELECT page_title, url, content FROM web_pages WHERE content = '$content';";

... $content doesn't appear to have been created beforehand; where do you expect to get this variable from? Seems like a logic problem too: if you've already got the page's content, you wouldn't need to query for it.

A common pattern for this sort of thing is using row IDs to fetch content. For example, you have the url "default.php?page_id=2" and you query for the content where ID is 2.

[dev2012]

I finally managed to at least stay on the same page at this point. Still don't know how to fetch the content. How do you do it?

//NAVIGATION
	$conn = mysqli_connect($host, $username, $password, $dbname) or die('Error connecting to MySQL server.');
	
	//select the url
	$sql = "SELECT * FROM web_pages;";
	$result = mysqli_query($conn, $sql) or die('Error querying database.');
	
	//loop through the page titles to populate the navigation bar
	while ($row = mysqli_fetch_array($result)) {
		$page_title = $row['page_title'];
		$url = $row['url'];
		$content = $row['content'];
		//echo "<ul><li><a href=' " . $row['id'] . " '> " . $row['page_title'] . "</a></li></ul>"; 
		echo '<a href="default.php?content='.$row["id"].'">'.$row["page_title"].'</a>';
	} 
	  
	mysqli_close($conn);


//CONTENT
$conn = mysqli_connect($host, $username, $password, $dbname) or die('Error connecting to MySQL server.');
					
//select the url
$sql = "SELECT * FROM web_pages WHERE id = ".$_GET['content'];
$result = mysqli_query($conn, $sql) or die('Error querying database.');
					
//loop through the page titles to populate the navigation bar
while ($row = mysqli_fetch_array($result)) {
	$id = $row['id'];
	$page_title = $row['page_title'];
	$url = $_GET['url'];
	$content = $row['content'];
}
					
if(!isset($_GET['id'])) {
	echo $row['page_title'];
	echo $row['content'];	
}
else
	echo "default.php";
	mysqli_close($conn);

[dev2012]

Here is my revised code:

I can get the default.php template stay put but my content is saying error querying database. I wonder why?

NAVIGATION

<?php
        //Connect to the db
        $conn = mysqli_connect($host, $username, $password, $dbname) or die('Error connecting to MySQL server.');
        
        //select the url
        $sql = "SELECT * FROM web_pages;";
        $result = mysqli_query($conn, $sql) or die('Error querying database.');
        
        //loop through the page titles to populate the navigation bar
        while ($row = mysqli_fetch_array($result)) {
        
                echo '<ul><li><a href="default.php?id='.$row["id"].'">'.$row["page_title"].'</a></li></ul>';
        } 
          
        mysqli_close($conn);
?>

CONTENT

<?php
$conn = mysqli_connect($host, $username, $password, $dbname) or die('Error connecting to MySQL server.');
                                        
//select the url
$sql = "SELECT * FROM web_pages WHERE id = $_GET[id]";
$result = mysqli_query($conn, $sql) or die('Error querying database.');                                 
                                        
//loop through the page titles to populate the content box
while ($row = mysqli_fetch_array($result)) {
        $id = $row['id'];
        $page_title = $row['page_title'];
        $url = $row['url'];
        $content = $row['content'];
}
mysqli_close($conn);
                                        
?>
                    
<?php 
        echo '<tr><td>' . $row['page_title'] . '</td>
        <td>' . $row['content'] . '</td>';
?>

[lintz]

Remove the ; after the query.

$sql = "SELECT * FROM web_pages";

[akhileshbc]

Try changing this line:

$sql = "SELECT * FROM web_pages WHERE id = $_GET[id]";

to:

$sql = "SELECT * FROM web_pages WHERE id = {$_GET['id']}";

Or to:

$id = $_GET['id'];
$sql = "SELECT * FROM web_pages WHERE id = $id";