Strange error with PHP exec command?

I just used exec command in PHP and I got this strange error. 1. I try to used php command like this : test1.php content :

if (!function_exists('json_decode')) {

$file = 'log.txt';
file_put_contents($file, "Fail to load JSON");
exit;

}else{

$file = 'log2.txt';
file_put_contents($file, "Success to load JSON");
exit;

}

In command line : >>php test1.php

I got Success to load JSON decode. But when i tried to run it like this: Test2.php content :

$test = exec( 'nohup n开发者_开发知识库ice php '.'test1.php');

I ran http://localhost/test2.php

Then I got Fail to load JSON decode .

That mean seem I can't get json_decode work within exec command ? What's happen and how to use json_decode within exec command ?

Is this the same host? Is it possible, that you run php test1.php on one machine, but script with exec on another? If so, then json_decode is only available since PHP 5.2.0. Check your PHP version by running this:

php -i | grep 'PHP Version'