Description:
------------
PHP 7.4.3 (cli)
Zend Engine v3.4.0
Kubuntu (focal) - x86_64
PHP_INT_SIZE:8 
PHP_INT_MAX:9223372036854775807

Created shared memeory with size 28991029248. Write in all diapozon is normal.
Read bigest at position 2147483646 one byte.
shmop_read($shmp, 2147483647, 1)
getted error 
Warning: shmop_read(): count is out of range in


Test script:
---------------
<?php
$KeyShm = ftok(__FILE__, 'a');
$shmp = shmop_open($KeyShm, 'n', 0644, 28991029248);
$WriteRes = shmop_write($shmp, "a", 2147483647);//All ok
$ReadRes1 = shmop_read($shmp, 2147483646, 1);//All ok
$ReadRes2 = shmop_read($shmp, 2147483647, 1);//Error 
//Warning: shmop_read(): count is out of range in
echo "ReadRes2:'".($ReadRes2!==false?$ReadRes2:'false')."' ".PHP_EOL;
shmop_delete($shmp);
shmop_close($shmp);


Expected result:
----------------
ReadRes2:'a'

Actual result:
--------------
ReadRes2:'false'