PHP 隐藏敏感字符

/**
 * 隐藏敏感字符
 * @param $value
 * @return string
 */
function substr_cut($value)
{
    $strlen = mb_strlen($value, 'utf-8');
    if ($strlen <= 1) return $value;
    $firstStr = mb_substr($value, 0, 1, 'utf-8');
    $lastStr = mb_substr($value, -1, 1, 'utf-8');
    return $strlen == 2 ? $firstStr . str_repeat('*', $strlen - 1) : $firstStr . str_repeat("*", $strlen - 2) . $lastStr;
}