Weird behavior of fetchAll() - PDO - php

Question

I am struggling with weird behavior of fetchAll(). I am executing a stored proc using PDO which returns the set of songs.
Here is my PHP code
$sql = "call getHymn(?)";
$param = array($id);
$result = $this->db->getData($sql,$param);
here is the getData function
public function getData($sql,$param=[])
{
try
{
$stmt = $this->connection->prepare($sql);
$stmt->execute($param);
echo '<pre>';
print_r($stmt->fetchAll());
/*return($stmt->fetchAll());*/
}
catch (PDOException $e)
{
throw new Exception($e->getMessage());
}
}
When I execute stored proc in MySQL it returns me 3 rows as expected. But when I execute it through PDO and use fetchall() then I get extra null outside the array..could not find any help anywhere, not even in PHP documentation. My fetchAll() output looks like below
Array
(
[0] => Array
(
[id] => 4
[refrain] =>
[stanzaId] => 1
[stanzaText] => Amazing grace! How sweet the sound
that saved a wretch like me!
I once was lost, but now am found;
was blind, but now I see.
)
[1] => Array
(
[id] => 4
[refrain] =>
[stanzaId] => 2
[stanzaText] => 'Twas grace that taught my heart to fear,
and grace my fears relieved;
how precious did that grace appear
the hour I first believed.
)
[2] => Array
(
[id] => 4
[refrain] =>
[stanzaId] => 3
[stanzaText] => Through many dangers, toils, and snares,
I have already come;
'tis grace hath brought me safe thus far,
and grace will lead me home
)
)
null
And here is my stored proc which is quite simple and straight forward
CREATE DEFINER=`root`#`localhost` PROCEDURE `getHymn`(IN `hid` INT)
READS SQL DATA
BEGIN
select
a.id, a.refrain, b.stanzaId, b.stanzaText
from
hymns a, hymnstanza b
where a.id = hid and a.id = b.hymnid;
END
Can anybody help me understand what is going on?

Answer 1

Okay, friends. I found the bug now and #decez you were absolutely correct that there was some extra echo statement which was causing null to appear after the array is printed. Feeling quite relaxed as after almost 12 hours I was able to move on successfully. THANK YOU ALL especially #decez.
Just to elaborate what mistake I had done, I was double JSONifying the output of fetchAll().