Description:
------------
I am running PHP 7.2.10 on CentOS 7.  If I run the below script file1.php, the memory usage gradually increases until it hits the memory limit.  The memory usage should remain relatively constant.  It's related to declaring the closure in file2.php, as if I remove the closure, then the memory usage stays constant.

Also, the memory usage stays constant in PHP 5.6, so the issue is perhaps only in PHP 7 and later.


Test script:
---------------
file1.php
<?php
for ($i = 0; $i < 1000000; $i++)
{
	echo $i.' - '.number_format(memory_get_usage())."\n";

	require('file2.php');
}


file2.php:
<?php
$test_function = function()
{
};


Expected result:
----------------
Memory usage stays constant.

Actual result:
--------------
Memory usage increases until it hits the memory limit.