请问一个异常Warning: rawurlencode() expects parameter 1 to be string, array given

请教一个错误Warning: rawurlencode() expects parameter 1 to be string, array given
Warning: rawurlencode() expects parameter 1 to be string, array given

PHP code

$normalized = array();
    foreach($params as $key => $val)
    {
        $normalized[] = $key."=".rawurlencode($val);
    }

参数$params为
array
  'auto' => int 123
  'on' => string '256855' (length=13)
  'ei' => string '' (length=0)
  'tm' => string '59.00' (length=5)
  'name' => string '' (length=0)
  'add' => string '' (length=0)
  'state' => int 1
  'list' => 
  array
  1 => string 'xxxxddewweew拾掇拾掇/59.00/1@' (length=68)

------解决方案--------------------
rawurlencode() expects parameter 1 to be string, array given
rawurlencode() 需要一个字符串类型的参数，你却传递了一个数组