JSON Web Token without third-party dependencies

simplejwt.php

<?php

function jwt_hs256_encode( $payload, $secret ) {

  $headers = array( 'alg' => 'HS256', 'typ' => 'JWT' );

  $parts[] = base64url_encode( json_encode( $headers, JSON_FORCE_OBJECT ) );
  $parts[] = base64url_encode( json_encode( $payload, JSON_FORCE_OBJECT ) );
  $signature = hash_hmac( 'SHA256', $parts[0] .'.'. $parts[1], $secret, true );
  $parts[] = base64url_encode( $signature );

  return implode( '.', $parts );
}

?>