SQL to determine Tablenames, Primarykeys & Foreignkeys]

Thanks to previous help I am using:
$sql = "SELECT " . "ic.relname AS index_name, " ."bc.relname AS tab_name, " . "ta.attname AS column_name, "
."i.indisuniqueAS unique_key, " ."i.indisprimary AS primary_key " .
 
"FROM " ."pg_class bc, " ."pg_class ic, " ."pg_index i, " ."pg_attribute ta, " ."pg_attribute ia " .
"WHERE " ."bc.oid = i.indrelid " ."AND ic.oid = i.indexrelid " ."AND ia.attrelid = i.indexrelid " ."AND ta.attrelid =
bc.oid" ."AND bc.relname = '" . $tablename . "' " ."AND ta.attrelid = i.indrelid " ."AND ta.attnum =
i.indkey[ia.attnum-1]" .
 
"ORDER BY " ."index_name, tab_name, column_name";
which provides primary keys 100%.
I have written the following to obtain tablenames:
$sql = "SELECT " . "ic.relname " .
"FROM " ."pg_class ic " .
"WHERE " ."ic.relname not like 'pg%' " ."AND ic.relname not like '%pk' " ."AND ic.relname not like '%idx' ";
which I am not certain is complete but appears to work.

Could anyone help me with the SQL to retrieve Foreign Keys for a
particular Table?

Much appreciated.
Kevin Gordon