Description:
------------
When use fread to read multiple small files with large buffer. 
it may make a memory limit error.

i think it becuase php alloc memory equals length that i send to fread and it not trim to actual size of string. so many small string can reach a memory limit.

or is it normal behavior?

Test script:
---------------
<?php
ini_set('memory_limit', '256M');
// create file
@mkdir('tmp_file');
for($i=0;$i<300;$i++){
file_put_contents("tmp_file/{$i}.txt", $i);
}
// read file
$data = [];
for($i=0;$i<300;$i++){
$fp = fopen("tmp_file/{$i}.txt", "r");
$data[$i] = fread($fp, 1024 * 1024);
fclose($fp);
echo strlen($data[$i])." ".memory_get_usage()."\n";
}

Expected result:
----------------
it can run normally. no memory allocate error.

Actual result:
--------------
Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 1048577 bytes)