Use PHP_VERSION_ID to check for the current php version

Signed-off-by: Daniel Kesselberg <mail@danielkesselberg.de>

lib/versioncheck.php

 <?php
 
 // Show warning if a PHP version below 7.2 is used,
-if (version_compare(PHP_VERSION, '7.2') === -1) {
+if (PHP_VERSION_ID < 70200) {
 	http_response_code(500);
 	echo 'This version of Nextcloud requires at least PHP 7.2<br/>';
 	echo 'You are currently running ' . PHP_VERSION . '. Please update your PHP version.';
@@ -9,7 +9,7 @@ if (version_compare(PHP_VERSION, '7.2') === -1) {
 }
 
 // Show warning if > PHP 7.4 is used as Nextcloud is not compatible with > PHP 7.4 for now
-if (version_compare(PHP_VERSION, '7.5.0') !== -1) {
+if (PHP_VERSION_ID >= 70500) {
 	http_response_code(500);
 	echo 'This version of Nextcloud is not compatible with > PHP 7.4.<br/>';
 	echo 'You are currently running ' . PHP_VERSION . '.';