Split a string in PHP into segments as array

string-segment-test.php

<?php

$output = [];
$lengthPerSegment = 40;
$string = "Hello, this is a string.";

foreach (str_split($string) as $index => $character) {
    if ($index % $lengthPerSegment === 0) {
        $output[] = substr($string, $index, $lengthPerSegment);
    }
}

echo print_r($output);