Description:
------------
mb_strimwidth returns an empty string for $width > 2147483647

mb_strimwidth requires memory greater than $width - 2GB for the provided test script

Affected versions (as far as I can test):
  - PHP 5.6.36-pl0-gentoo (cli and fpm)
  - PHP 7.2.6 (cli and fpm)
 

Test script:
---------------
<?php

declare(strict_types=1);

function doIt(int $width): void
{
    $string_to_trim = 'some test string';
    $expected_result = $string_to_trim;
    $actual_result = mb_strimwidth($string_to_trim, 0, $width);

    echo <<<RESULT
Width:             $width
String to trim:    $string_to_trim
Expected result:   $expected_result
Acutal result:     $actual_result


RESULT;
}

$width = 2147483647;
doIt($width);
doIt($width + 1);

echo memory_get_peak_usage(true);


Expected result:
----------------
Width:             2147483647
String to trim:    some test string
Expected result:   some test string
Acutal result:     some test string

Width:             2147483648
String to trim:    some test string
Expected result:   some test string
Acutal result:     some test string

2149580800

Actual result:
--------------
Width:             2147483647
String to trim:    some test string
Expected result:   some test string
Acutal result:     some test string

Width:             2147483648
String to trim:    some test string
Expected result:   some test string
Acutal result:     

2149580800