retrieving a record and displaying it?

[abcd1234]

hi, i'm trying to retrieve a record using this codes below,
is these codes correct?

	
$sql->QueryRow("select * from photos where photo_filename = $cur_file");
	$row = $sql->data;

$max_array = count($row);
echo $row[id];

These codes is showing me this error.

Fatal error: Call to a member function on a non-object in /home/askjames/public_html/mygallery/img_info.php on line 30

Line 30 is the first line of code that i have posted.

Please tell me what is going on with these codes?
I hope you can help me, Thank you very much in advance.

[halojoy]

you have not installed class and created class object $sql

include ( 'database.class.php' );
$sql = new database();