<?php
$encoding        = 'ASCII';
$known_encodings = mb_list_encodings();

if (in_array($encoding, $known_encodings)) {

    $aliases = mb_encoding_aliases($encoding);
    print_r($aliases);

} else {

    echo "Unknown ($encoding) encoding.\n";

}
?>

   

ENTITY

Array
(
    [0] => ANSI_X3.4-1968
    [1] => iso-ir-6
    [2] => ANSI_X3.4-1986
    [3] => ISO_646.irv:1991
    [4] => US-ASCII
    [5] => ISO646-US
    [6] => us
    [7] => IBM367
    [8] => cp367
    [9] => csASCII
)