为什么PHP可以将％2B转换为空字符串而不是+？

I am runing Laravel 5.3 application on PHP buildin-server and trying to perform following request:

api/people?sort=%2Bname

I expect that %2B will be converted to +, but for some reasons, it doesn't happen:

$request->input('sort') => " name"

Can such behaviour be related to PHP settings?

Seems a PHP thing, test it with:

print_r(rawurldecode($_SERVER['QUERY_STRING']));//Result:content=+name

and

print_r(urldecode($_SERVER['QUERY_STRING']));//Result:content= name

Workaround:

$result=array();
array_map(function($a) use (&$result){
              $a=explode('=',$a);        
              $result[$a[0]]=$a[1];
},explode('&',rawurldecode($_SERVER['QUERY_STRING'])));

print_r($result);