print_r ends with a newline if you print_r() an array, but not if you print_r() a string or number:

$foo="abc";
$bar=123;
echo "-";
print_r($foo);
echo "-";
print_r($bar);
echo "-";

Ouput: -abc-123-


$foo=array(123, "abc");
echo "-";
print_r($foo);
echo "-";

Output: 
-Array
(
    [0] => 123
    [1] => abc
)
-