PHP如何将一个字符串部分字符用星号替代隐藏？

<?php 
 
/**
 +----------------------------------------------------------
 * 将一个字符串部分字符用*替代隐藏
 +----------------------------------------------------------
 * @param string $string 待转换的字符串
 * @param int  $bengin 起始位置，从0开始计数，当$type=4时，表示左侧保留长度
 * @param int  $len  需要转换成*的字符个数，当$type=4时，表示右侧保留长度
 * @param int  $type  转换类型：0，从左向右隐藏；1，从右向左隐藏；2，从指定字符位置分割前由右向左隐藏；3，从指定字符位置分割后由左向右隐藏；4，保留首末指定字符串
 * @param string $glue  分割符
 +----------------------------------------------------------
 * @return string 处理后的字符串
 +----------------------------------------------------------
 */
function hideStr($string, $bengin = 0, $len = 4, $type = 0, $glue = "@") {
if (empty($string))
return false;
$array = array();
if ($type == 0 || $type == 1 || $type == 4) {
$strlen = $length = mb_strlen($string);
while ($strlen) {
$array[] = mb_substr($string, 0, 1, "utf8");
$string = mb_substr($string, 1, $strlen, "utf8");
$strlen = mb_strlen($string);
}
}
if ($type == 0) {
for ($i = $bengin; $i < ($bengin + $len); $i++) {
if (isset($array[$i]))
$array[$i] = "*";
}
$string = implode("", $array);
} else if ($type == 1) {
$array = array_reverse($array);
for ($i = $bengin; $i < ($bengin + $len); $i++) {
if (isset($array[$i]))
$array[$i] = "*";
}
$string = implode("", array_reverse($array));
} else if ($type == 2) {
$array = explode($glue, $string);
$array[0] = hideStr($array[0], $bengin, $len, 1);
$string = implode($glue, $array);
} else if ($type == 3) {
$array = explode($glue, $string);
$array[1] = hideStr($array[1], $bengin, $len, 0);
$string = implode($glue, $array);
} else if ($type == 4) {
$left = $bengin;
$right = $len;
$tem = array();
for ($i = 0; $i < ($length - $right); $i++) {
if (isset($array[$i]))
$tem[] = $i >= $left ? "*" : $array[$i];
}
$array = array_chunk(array_reverse($array), $right);
$array = array_reverse($array[0]);
for ($i = 0; $i < $right; $i++) {
$tem[] = $array[$i];
}
$string = implode("", $tem);
}
return $string;
}
 
 
$str = '12345678901';
echo hideStr($str,2,4);

$username = "linshouyue"; 
echo substr_replace($username,'****','3','4');

/**     * *替换中文汉字
     * @author 月月
     */
    function substr_cut($user_name){
        $strlen     = mb_strlen($user_name, 'utf-8');
        $firstStr     = mb_substr($user_name, 0, 1, 'utf-8');
        $lastStr     = mb_substr($user_name, -1, 1, 'utf-8');
        return $strlen == 2 ? $firstStr . str_repeat('*', mb_strlen($user_name, 'utf-8') - 1) : $firstStr . str_repeat("*", $strlen - 2) . $lastStr;
    }