Site Health: Correct the check for disk space available to safely per…

…form updates.

If the available disk space exceeds the `PHP_INT_MAX` value, i.e. a 32-bit PHP version is in use with more than 2 GB free, the type casting to `(int)` could cause an overflow, and the Site Health test would then erroneously report that there is not enough free space. 

This commit removes the unnecessary type casting and uses the result from `disk_free_space()` directly.

Includes optimizing the logic to skip further checks if the available disk space could not be determined.

Follow-up to [55720].

Props mathsgrinds, Presskopp, rajinsharwar, SergeyBiryukov.
Fixes #59116.

git-svn-id: https://develop.svn.wordpress.org/trunk@56401 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/class-wp-site-health.php

@@ -1943,10 +1943,6 @@ public function get_test_plugin_theme_auto_updates() {
 	public function get_test_available_updates_disk_space() {
 		$available_space = function_exists( 'disk_free_space' ) ? @disk_free_space( WP_CONTENT_DIR . '/upgrade/' ) : false;
 
-		$available_space = false !== $available_space
-			? (int) $available_space
-			: 0;
-
 		$result = array(
 			'label'       => __( 'Disk space available to safely perform updates' ),
 			'status'      => 'good',
@@ -1963,18 +1959,14 @@ public function get_test_available_updates_disk_space() {
 			'test'        => 'available_updates_disk_space',
 		);
 
-		if ( $available_space < 100 * MB_IN_BYTES ) {
-			$result['description'] = __( 'Available disk space is low, less than 100 MB available.' );
+		if ( false === $available_space ) {
+			$result['description'] = __( 'Could not determine available disk space for updates.' );
 			$result['status']      = 'recommended';
-		}
-
-		if ( $available_space < 20 * MB_IN_BYTES ) {
+		} elseif ( $available_space < 20 * MB_IN_BYTES ) {
 			$result['description'] = __( 'Available disk space is critically low, less than 20 MB available. Proceed with caution, updates may fail.' );
 			$result['status']      = 'critical';
-		}
-
-		if ( ! $available_space ) {
-			$result['description'] = __( 'Could not determine available disk space for updates.' );
+		} elseif ( $available_space < 100 * MB_IN_BYTES ) {
+			$result['description'] = __( 'Available disk space is low, less than 100 MB available.' );
 			$result['status']      = 'recommended';
 		}