3v4l.org

run code in 300+ PHP versions simultaneously
<?php $subusers = [" hey", " h i", " ", "wh@t"]; foreach ($subusers as $subuser) { echo "Assess \"$subuser\":\t"; if (!strlen($subuser = trim($subuser))) { echo "* Username not entered"; //} elseif (!preg_match('/^[\da-z]+$/i', $subuser)) { } elseif (!ctype_alnum($subuser)) { echo "* Username not alphanumeric"; } echo "\n"; }
Output for 5.6.38, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 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
Assess " hey": Assess " h i": * Username not alphanumeric Assess " ": * Username not entered Assess "wh@t": * Username not alphanumeric

preferences:
168.19 ms | 403 KiB | 197 Q