My PHP has some bugs on json_decode()? Can't decode String or Number literals not covered with Array or Object.

01_json_test.php

<?php
$testCases = array(
    '[1,2,3]',
    '{"one":1,"two":2,"three":3}',
    '"1"',  
    '1'
);

foreach ($testCases as $testCase) {
    echo "INPUT:", PHP_EOL;
    echo $testCase, PHP_EOL;
    echo "OUTPUT:", PHP_EOL;
    var_dump(json_decode($testCase));
    echo PHP_EOL;
}

02_result_on_my_server.txt

$ php -v
PHP 5.2.0-8+etch16 (cli) (built: Nov 24 2009 06:58:21) 
Copyright (c) 1997-2006 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2006 Zend Technologies

$ php -i | grep json
json
json support => enabled
json version => 1.2.1

$ php json.php 
INPUT:
[1,2,3]
OUTPUT:
array(3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
}

INPUT:
{"one":1,"two":2,"three":3}
OUTPUT:
object(stdClass)#1 (3) {
  ["one"]=>
  int(1)
  ["two"]=>
  int(2)
  ["three"]=>
  int(3)
}

INPUT:
"1"
OUTPUT:
NULL

INPUT:
1
OUTPUT:
NULL

03_result_on_another_server.txt

$ php -v
PHP 5.3.2-1ubuntu4.5 with Suhosin-Patch (cli) (built: Sep 17 2010 13:41:55) 
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies

$ php -i | grep json
json
json support => enabled
json version => 1.2.1

$ php json_test.php 
INPUT:
[1,2,3]
OUTPUT:
array(3) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
}

INPUT:
{"one":1,"two":2,"three":3}
OUTPUT:
object(stdClass)#1 (3) {
  ["one"]=>
  int(1)
  ["two"]=>
  int(2)
  ["three"]=>
  int(3)
}

INPUT:
"1"
OUTPUT:
string(1) "1"

INPUT:
1
OUTPUT:
int(1)