解决php中字符串输出一样但比较不相等（编码不同导致长度不一样）

header("Content-type:text/html;charset=utf-8");
$secret1 = "rZa9GneIzd9MNyoTv/Ghpk2V6ZHD0KeQC7t0ymEH7cI=";
$secret2 = 'rZa9GneIzd9MNyoTv/Ghpk2V6ZHD0KeQC7t0ymEH7cI=';
$secret3 = 'rZa9GneIzd9MNyoTv/Ghpk2V6ZHD0KeQC7t0ymEH7cI=';
var_dump(trim($secret1));
echo "<br>";
var_dump(trim($secret2));
echo "<br>";
var_dump($secret3);
echo "<br>";
echo mb_detect_encoding($secret1, array("ASCII", "UTF-8", "GB2312", "GBK", "BIG5"));
echo "<br>";
echo mb_detect_encoding($secret2, array("ASCII", "UTF-8", "GB2312", "GBK", "BIG5"));
echo "<br>";
echo mb_detect_encoding($secret3, array("ASCII", "UTF-8", "GB2312", "GBK", "BIG5"));

function removeBom($string)//去除BOM
{
  if (substr($string, 0, 3) == pack("CCC", 0xef, 0xbb, 0xbf)) {
    return substr($string, 3);
  }
  return $string;
}
function ConvertUTF8ToGB2312($str)//转化为统一编码;
{
  return iconv("UTF-8", "GB2312//IGNORE", $str);
}