booleans

Good day all,

I just wrote an HTML form with a PHP script to enter data into a table 
witha boolean field.  When I pressed enter it returned the following error
"Warning: PostgresSQL query failed: ERROR: Bad boolean external 
representation".  The script is as follows:

if( $id ) {
        pg_Exec($conn, "INSERT into authors
        VALUES ('$pubrelease', '$id', '$first');");
        }

I would appreciate any help.

Thanks,

-Greg