$str = encode_str("19876");

echo '<br/>'.$str.'<br/>' ;

echo decode_str($str);

function encode_str($str) {

}

function decode_str($str) {

}

<script type="text/javascript">

var encod = encode_str('19');

console.log(encod)

console.log(decode_str(encod))

function encode_str(str) {

var encoded = '';

var alpha_map = ['P', 'M', 'S', 'K'];

var str = str.toString();

var len = str.length;

var ascii_arr = [];

var salt = 150;//rand(100, (999 - 255));

for (var x = 0; x < len; x++) {

ascii_arr[x] = (rand(1, 9) * 1000) + (salt + str.charCodeAt(x));

}

var enc = ascii_arr.join('') + salt;

var enc_len = enc.length;

for (var x = 0; x < enc_len; x++) {

if (typeof(alpha_map[enc[x]]) != 'undefined') {

encoded += alpha_map[enc[x]];

} else {

encoded += enc[x];

}

}

return encoded.toLowerCase();

}

function decode_str(str) {

str = str.toUpperCase();

var unit_size = 4;

var alphatonum = function(s) {

var alpha_map = ['P', 'M', 'S', 'K'];

var l = s.length;

var s_ = '';

for (var x = 0; x < l; x++) {

var pos = alpha_map.indexOf(s[x]);

s_ += (pos >= 0) ? pos : s[x];

}

return s_;

};

var decoded = '';

var salt = alphatonum(str.substr(-3));

var data = alphatonum(str.substr(0, (str.length - 3)));

var loop = data.length / unit_size;

for (var x = 0; x < loop; x++) {

var unit = data.substr(x * unit_size, unit_size);

var ascii_ = (unit % 1000) - salt;

decoded += String.fromCharCode(ascii_)

}

return decoded;

}

function rand(x, y) {

return parseInt(Math.random() * (y + 1 - x) + x, 10);

}

</script>