Firebird procedure is not performed only in PDO

Question

I have a Firebird procedure:

CREATE OR ALTER procedure INSERT_LABELS_SET (
    IN_NAME varchar(50))
returns (
    OUT_ID smallint)
as
begin
    IF ((SELECT COUNT(*) FROM labels_sets WHERE name=:in_name) = 0) THEN
    INSERT INTO labels_sets(name) VALUES (:in_name) RETURNING id into :out_id;
suspend;
end

When I try to execute it in PHP:

/**
 * @var $stmt PDOStatement
 */
$stmt = $this->db->prepare('EXECUTE PROCEDURE insert_labels_set(?);');
$stmt->execute(array($value));

I get an error:

SQLSTATE[HY000]: General error: -804 Dynamic SQL Error SQL error code = -804 Incorrect values within SQLDA structure

How can I fix the error?

Such problem is only in PDO. When I use ibase_connect() everything works perfectly.

Answer 1

Solution:

$stmt = $this->db->prepare('SELECT OUT_ID from insert_labels_set(?);');
$stmt->execute(array($value));

But why didn't work the previous version, I don't understand