fwrite无法在包含文件中工作

I have one php file "test.php" which have below code

$file = fopen("../testwrite.php","w");
echo fwrite($file,"<h1>this is for testing</h1>");
fclose($file);

now I have one more php file named original.php in which I have included test.php. But when I run original.php then fwrite function have no affect. "testwrite.php" is not writing.

but if I direct run test.php then it is working and testwrite.php will write but content.

content of original.php is below,

<?php include_once 'test.php'; 

// other process ?>

So what is issue here?