php字符串超长自动换行

1. 英文字符串超长换行使用系统方法wordwrap

2. 中文字符串超长换行自行定义方法mb_wordwrap

    /**
     * Notes:对传入的中文字符串处理，如果字符串超过限定的长度，则自动进行换行
     * docs:
     */
    function mb_wordwrap($str, $width = 8, $break = "\r\n"){
        // Return short or empty strings untouched
        if (empty($str) || mb_strlen($str, 'UTF-8') <= $width) {
            return $str;
        }

        $br_width = mb_strlen($break, 'UTF-8');
        $str_width = mb_strlen($str, 'UTF-8');
        $return = '';
        $last_space = false;

        for ($i = 0, $count = 0; $i < $str_width; $i++, $count++) {
            // If we're at a break
            if (mb_substr($str, $i, $br_width, 'UTF-8') == $break) {
                $count = 0;
                $return .= mb_substr($str, $i, $br_width, 'UTF-8');
                $i += $br_width - 1;
                continue;
            }

            // Keep a track of the most recent possible break point
            if (mb_substr($str, $i, 1, 'UTF-8') == " ") {
                $last_space = $i;
            }

            // It's time to wrap
            if ($count > $width) {
                // There are no spaces to break on!  Going to truncate :(
                if (!$last_space) {
                    $return .= $break;
                    $count = 0;
                } else {
                    // Work out how far back the last space was
                    $drop = $i - $last_space;

                    // Cutting zero chars results in an empty string, so don't do that
                    if ($drop > 0) {
                        $return = mb_substr($return, 0, -$drop);
                    }

                    // Add a break
                    $return .= $break;

                    // Update pointers
                    $i = $last_space + ($br_width - 1);
                    $last_space = false;
                    $count = 0;
                }
            }

            // Add character from the input string to the output
            $return .= mb_substr($str, $i, 1, 'UTF-8');
        }
        return $return;
    }