Solution 1:
Disable all plugins. And then try upgrading wordpress
Solution 2:
Open wp-config.php file in the root directory of wordpress installation and add define(‘WP_MEMORY_LIMIT’, ’64M’); at the very beginning after
Solution 3:
Open wp-settings.php file in the root folder of wordpress installation.
Change 32M to 64M in line 13
Solution 4:
Manual Upgradation. Download the zip file, extract it and upload to your server.
