prep.php

<?php
/** Prepare a string for use with wordwrap by hyphenate words longer that $width
 *
 * Example:
 *     echo prep("1 12 123 1234 12345 123456 1234567 12345678", 4), PHP_EOL;
 * Outputs:
 *     1 12 123 123-4 123-45 123-456 123-4567 123-456-78
 * XXX: DO NOT USE THIS UNLESS YOU KNOW YOU CAN(See for example preg_quote()).
 */
function prep($str, $width=72) {
    $old = null;
    $new = $str;
    $limit = $width - 1;
    while ($old !== $new) {
        $old = $new;
        $new = preg_replace("/([a-z0-9]{{$limit},{$limit}})([a-z0-9]{2,})/i", "\\1-\\2", $old);
    }
    return $new;
}