rtrim function doesn't work with ending h letter

Question

$file = \"refinish.php\";
$folder = rtrim($file, \".php\");
echo $folder; // refinis

where is ending h ?

I tried with some other

Answer 1

How rtrim() works

$file = "finish.php";
$folder = rtrim($file, ".php");

is processed working through the characters in $file from the last character backwards as

$file = "finish.php";
//                ^
//     Is there a `p` in the list of characters to trim

$folder = rtrim($file, ".php");
//                       ^
//     Yes there is, so remove the `p` from the `$file` string

$file = "finish.ph";
//               ^
//     Is there a `h` in the list of characters to trim

$folder = rtrim($file, ".php");
//                        ^
//     Yes there is, so remove the `h` from the `$file` string

$file = "finish.p";
//              ^
//     Is there a `p` in the list of characters to trim

$folder = rtrim($file, ".php");
//                       ^
//     Yes there is, so remove the `p` from the `$file` string

$file = "finish.";
//             ^
//     Is there a `.` in the list of characters to trim

$folder = rtrim($file, ".php");
//                      ^
//     Yes there is, so remove the `.` from the `$file` string

$file = "finish";
//            ^
//     Is there a `h` in the list of characters to trim

$folder = rtrim($file, ".php");
//                        ^
//     Yes there is, so remove the `h` from the `$file` string

$file = "finis";
//           ^
//     Is there a `s` in the list of characters to trim

$folder = rtrim($file, ".php");
//                      ????
//     No there isn't, so terminate the checks and return the current value of `$file`

$file = "finis";