I can't reproduce https://3v4l.org/kEBSX and it sounds weird.

Please can you test again with opcache disabled, if it's currently enabled.

Also please try with all other extensions disabled.

Also, this has a very small chance of being a weird interaction between your terminal and the bytes. Please could you run this to see what implode is actually doing.

function getRawCharacters($result) {
    $resultInHex = unpack('H*', $result);
    $resultInHex = $resultInHex[1];
    $resultSeparated = implode(', ', str_split($resultInHex, 2));
    return $resultSeparated;
}

$ar = [12345678, 12345678, 12345678, 3, 4, 5, 6, 7, 8];
$string = implode(chr(9), $ar);

echo getRawCharacters($string) . PHP_EOL;

The problem is not PHP-related. It is a problem wit Apple's Terminal.app. The string output by the bash command

echo -e '12345678\t12345678\t12345678\t3\t4\t5\t6\t7\t8'

depends on the Terminal windows's width.

So I owe an apology to PHP's implode function.

Thanks to everybody. Bug should be closed.