string - How to convert all characters to their html entity equivalent using PHP

Question

I want to convert this hello@domain.com to

hello@domain.com

I have tried:

url_encode($string)

this provides the same string I entered, returned with the @ symbol converted to %40

also tried:

htmlentities($string)

this provides the same string right back.

I am using a UTF8 charset. not sure if this makes a difference....

Answer 1

Here it goes (assumes UTF-8, but it's trivial to change):

function encode($str) {
    $str = mb_convert_encoding($str , 'UTF-32', 'UTF-8'); //big endian
    $split = str_split($str, 4);

    $res = "";
    foreach ($split as $c) {
        $cur = 0;
        for ($i = 0; $i < 4; $i++) {
            $cur |= ord($c[$i]) << (8*(3 - $i));
        }
        $res .= "&#" . $cur . ";";
    }
    return $res;
}

EDIT Recommended alternative using unpack:

function encode2($str) {
    $str = mb_convert_encoding($str , 'UTF-32', 'UTF-8');
    $t = unpack("N*", $str);
    $t = array_map(function($n) { return "&#$n;"; }, $t);
    return implode("", $t);
}