3v4l.org

run code in 300+ PHP versions simultaneously
<?php if(!isset($_SESSION['user'])){ echo('<a href="user/register.php"><span class="signbutton" style="background-color:aqua;">Registrovat se</span></a> <a href="user/login.php"><span class="signbutton">Přihlásit se</span></a>'); }else{ echo('Přihlášen: '.$_SESSION['user']); } ?>
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.35, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
<a href="user/register.php"><span class="signbutton" style="background-color:aqua;">Registrovat se</span></a> <a href="user/login.php"><span class="signbutton">Přihlásit se</span></a>

preferences:
194.41 ms | 406 KiB | 339 Q