function obfuscate_email($email)
{
$em = explode("@",$email);
$name = implode('@', array_slice($em, 0, count($em)-1));
$len = floor(strlen($name)/2);

return substr($name,0, $len) . str_repeat('*', $len) . "@" . end($em);
}

// to see in action:
$emails = ['"Abc@def"@iana.org', 'abcdlkjlkjk@hotmail.com'];

foreach ($emails as $email)
{
echo obfuscate_email($email) . "n";
}