100分求个 检拆字符串长度

100分求个 检测字符串长度
$str[0] = "123asd你好[哈哈]"
$str[1] = "123asd你好[你好不好啊]"
//一个中文一个字符(utf-8的编码) 符号 [这里面的字和外边的符号算一个字符] 
然后计算长度
结果是$str[0]和$str[1]为长度9

最好写成一个函数。谢谢了


------解决方案--------------------
我没太看懂楼主的题，不过函数，手头上有一个。

PHP code

/**
     * 得到utf8 的长度
     * @author mu_rain
     * @param String $str
     * @return Int
     */
    static function strlen_utf8($str) {
        $i = 0;
        $count = 0;
        $len = strlen ($str);
        while ($i = $len) break;
            if($chr & 0x80) {
                $chr <font color="#e78608">------解决方案--------------------</font><br>

PHP code

    function myLen($str,$startTag='[',$endTag=']',$encoding='utf-8')
    {
        $st = preg_quote($startTag);
        $et = preg_quote($endTag);
        return mb_strlen(preg_replace("#{$st}[^{$et}]*{$et}#","~",$str),$encoding);
    }
echo myLen("123asd你好[哈哈]");//9
<br><font color="#e78608">------解决方案--------------------</font><br>附赠字符串函数一堆　，慢用。<br>

PHP code

<?php /**
 * Created by JetBrains PhpStorm.
 * User: Administrator
 * Date: 12-2-17
 * Time: 上午11:43
 * To change this template use File | Settings | File Templates.
 */
/**
 * 字符串处理基类.
 * @author mu_rain
 */
class kString{
    // ------------------------------------
    /**
     * replace  the base64_encode to encode the string
     *
     * @param  $str    对象的实例
     * @package   KDG
     * @subpackage    String
     * @category    Putils
     * @author        jim
     *  @return mixed
     */
    // ------------------------------------
    public static function encode($str){
        $src  = array("/","+","=");
        $dist = array("-a","-b","-c");
        $old  = base64_encode($str);
        $new  = str_replace($src,$dist,$old);
        return $new;
    }

    // ------------------------------------
    /**
     * replace  the base64_decode to decode the string
     *
     * @param  $str    对象的实例
     * @package        P
     * @subpackage    String
     * @category    Putils
     * @author        jim
     *  @return mixed
     */
    // ------------------------------------
    public static function decode($str){
        $src = array("-a","-b","-c");
        $dist  = array("/","+","=");
        $old  = str_replace($src,$dist,$str);
        $new = base64_decode($old);
        return $new;
    }



    // ------------------------------------
    /**
     * replace  the base64_decode to decode the string
     *
     * @param  $str    对象的实例
     * @package        P
     * @subpackage    String
     * @category    Putils
     * @author        jim
     *  @return mixed
     */
    // ------------------------------------
    public static function showAsFileSize($str){ // change 1024 to 1k
        $count = intVal($str);
        $destSize = $count/1024;
        $destSize = round($destSize,1);
        return $destSize."K";
    }




} <div class="clear">