เข้ารหัสของ RSA (cryptosystem) outputออกมาเป็นอักษรขยะ

<?php
$plaintext = "Helloworld";
echo encrypt_RSA($plaintext);
// 1778686828772858572948091 
function encrypt_RSA($text)
{
    $a = [];
    $b = [];
    $p = 0;
    $q = 0;
     while (true) {
         $p = rand(1, 30);
     if (findPrime($p) == true) {
             break;
         }
     }

     while (true) {
         $q = rand(1,30);
        if (findPrime($q) == true) {
             break;
        }
     }

    $n = $p * $q;
    while (true) {
        $n1 = (($p - 1) * ($q - 1));
        $e = rand(1, $n1);

        if (gcd($e, $n1) == 1) {
            break;
        }
    }

    echo "Public key: " . $n . " , " . $e;
    print("\n");

    for ($i = 0; $i < $n1 - 1; $i++) {
        if (($i * $e) % $n1 == 1) {
            (float)$d = $i;
            break;
        }
    }
    echo "Private key: " . $d;


    for ($i = 0; $i < strlen($text); $i++) {
        $t = toNum($text[$i]);
        $t = myPowMod($t, $e, $n);
        array_push($a, $t);

        $t = toText($t);
        array_push($b, chr($t));
    }

    for ($x = 0; $x < count($a); $x++) {
        echo $a[$x] . "";
    }

    print("\n");
    for ($x = 0; $x < count($b); $x++) {
        echo $b[$x] . "";
    }
    print("\n");
    $a = null;
    $b = null;
}

function decrypt_RSA($text)
{
    $a = [];
    $b = [];
    $p = 0;
    $q = 0;
    $textLength = strlen($text);
    $textN=[];
    while (true) {
        $p = rand(1, 50);
        if (findPrime($p) == true) {
            break;
        }
    }

    while (true) {
        $q = rand(1, 50);
        if (findPrime($q) == true) {
            break;
        }
    }

    $n = $p * $q;
    while (true) {
        $n1 = ($p - 1) * ($q - 1);
        $e = rand(1, $n1);

        if (gcd($e, $n1) == 1) {
            break;
        }
    }
    echo "Public key: " . $n . " , " . $e;
    print("\n");

    for ($i = 0; $i < $n1 - 1; $i++) {
        if (($i * $e) % $n1 == 1) {
            (float)$d = $i;
            break;
        }
    }
    echo "Private key: " . $d;
    $textLength = strlen($text);
    $textN=[];

    for ($i = 0; $i < strlen($text); $i++) {
        $t = toNum($text[$i]);
        $t = myPowMod($t, $e, $n);
        $t = toText($t);
        echo chr($t);
       
    }
   

    //echo $b . "";
    // print_r($t);
   // print("\n");
  




    return 0;
}


function toNum($a)
{
    $a = ord($a) - (ord('z') - ord('a'));
    return $a;
}


function toText($a)
{
    $a = $a + (ord('z') - ord('a'));
    return $a;
}



function myPowMod($a, $b, $c)
{

    $x = 1;
    $a = $a % $c;
    if ($a == 0) {
        return 0;
    }
    while ($b > 0) {
        if (($b & 1) == 1) {
            $x = ($x * $a) % $c;
        }

        $b = (int)($b / 2);
        $a = ($a * $a) % $c;
    }
    return $x;
}

function gcd($a, $b)
{
    if ($a > $b) {
        $small = $b;
    } else {
        $small = $a;
    }
    for ($i = 1; $i < $small + 1; $i++) {
        if (($a % $i == 0) && ($b % $i == 0)) {
            $gcd = $i;
        }
    }


    return $gcd;
}


function findPrime($a)
{
    for ($i = 2; $i < $a - 1; $i++) {
        if ($a % $i == 0) {
            return 0;
        }
    }
    return 1;
}