PHP - Mostrar caracteres especiales al cifrarlos

<?php

header ("Content-Type: text/plain; charset=UTF-8");

mb_internal_encoding("UTF-8");

mb_http_output( "UTF-8" );

ob_start("mb_output_handler");

echo utf8_encode($data);

echo utf8_decode($data);

<?php

header ("Content-Type: text/plain; charset=UTF-8");

mb_internal_encoding("UTF-8");

mb_http_output( "UTF-8" );

ob_start("mb_output_handler");

function Cript($strOld, $bcode){

$resultado = "";

$target = $strOld;

$total = strlen($target);

for ($x = 0; $x < $total; $x++) {

$char = ord (substr($strOld,$x,1));

$CriptChar = $char ^ $bcode;

$CriptChar = utf8_encode(chr($CriptChar));

$resultado = $resultado .$CriptChar;

if ( $x === $total - 1){

echo mb_detect_encoding($resultado).PHP_EOL;

$cifrado = $resultado;

$file = fopen("output.txt", "w");

fwrite($file,$cifrado);

fclose($file);

return $resultado;

}

}

}

echo Cript("Hola mundo","123");

echo PHP_EOL.mb_internal_encoding();

?>