PHP encryption method

Encr.php

<?php

/**
 * @property  string
 */
function encr($raw) {
    $encoded = "";
    $seprated = str_split(base64_encode($raw));
    $empty = [];
    while (count($seprated) > 0) {
        $encoded .= $seprated[0];
        unset($seprated[0]);
        foreach($seprated as $i) {
            $empty[] = $i;
        }
        $seprated = $empty;
        $empty = [];
        if (count($seprated) > 0) {
            $encoded .= $seprated[count($seprated) - 1];
            unset($seprated[count($seprated) - 1]);
            foreach($seprated as $i) {
                $empty[] = $i;
            }
            $seprated = $empty;
            $empty = [];
        }
    }
    return $encoded;
}
function decr($encr) {
    $seprated = str_split($encr);
    $empty = [];
    $index = 0;
    $reverse = count($seprated) - 1;
    foreach($seprated as $i=>$v) {
        if ($i%2 == 0) {
            $empty[$index] = $v;
            $index++;
        } else {
            $empty[$reverse] = $v;
            $reverse--;
        }
    }
    ksort($empty);
    $decoded = implode("", $empty);
    return base64_decode($decoded);
}
$hello = encr("Hello!");
echo $hello;
echo decr($hello);