mb_str_pad.php

<?php

/**
 * Multibyte String Pad
 *
 * Functionally, the equivalent of the standard str_pad function, but is capable of successfully padding multibyte strings.
 *
 * @param string $input The string to be padded.
 * @param int $pad_length The length of the resultant padded string.
 * @param string $pad_string The string to use as padding. Defaults to space.
 * @param int $pad_type The type of padding. Defaults to STR_PAD_RIGHT.
 * @param string $encoding The encoding to use, defaults to UTF-8.
 *
 * @return string A padded multibyte string.
 */
function mb_str_pad(string $input, int $pad_length, string $pad_string = "\x20", int $pad_type = STR_PAD_RIGHT, string $encoding = 'UTF-8')
{
    $input_length = mb_strlen($input, $encoding);
    $pad_string_length = mb_strlen($pad_string, $encoding);

    if ($pad_length <= 0 || ($pad_length - $input_length) <= 0) {
        return $input;
    }

    $num_pad_chars = $pad_length - $input_length;

    switch ($pad_type) {
        case STR_PAD_RIGHT:
            $left_pad = 0;
            $right_pad = $num_pad_chars;
            break;

        case STR_PAD_LEFT:
            $left_pad = $num_pad_chars;
            $right_pad = 0;
            break;

        case STR_PAD_BOTH:
            $left_pad = floor($num_pad_chars / 2);
            $right_pad = $num_pad_chars - $left_pad;
            break;
    }

    $result = '';
    for ($i = 0; $i < $left_pad; ++$i) {
        $result .= mb_substr($pad_string, $i % $pad_string_length, 1, $encoding);
    }
    $result .= $input;
    for ($i = 0; $i < $right_pad; ++$i) {
        $result .= mb_substr($pad_string, $i % $pad_string_length, 1, $encoding);
    }

    return $result;
}