Javascript function in PHP fromCharCode()

Try the chr() function:

Returns a one-character string containing the character specified by ascii.

http://php.net/manual/en/function.chr.php

PHP has chr function which would return one-character string containing the character specified by ascii

To fit your java script style you can create your own class

$string = String::fromCharCode(112, 108, 97, 105, 110);
print($string);

Class Used

class String {
    public static function fromCharCode() {
        return array_reduce(func_get_args(),function($a,$b){$a.=chr($b);return $a;});
    }
}