If you are able to upload small files with PHP script but unable to upload larger files it means you will need to increase upload_max_filesize limit in your php.in file.
In this article I will show how you can increase upload_max_filesize for your website.
PHP has several configuration options to limit resources consumed by scripts. By default, PHP is set to allow uploads of files with a size of 2MB or less.
Increase PHP Upload Limits
Try increasing the following values in php.ini, for example:
memory_limit = 20M upload_max_filesize = 12M post_max_size = 20M
After making these changes, you may need to restart Apache. You can do so through Plesk or via SSH with the following command:
# /etc/init.d/httpd restart
If the upload_max_filesize is larger than post_max_size, you must increase post_max_size so that it is bigger than upload_max_size.
If the value of post_max_size is larger than memory_limit, you must increase memory_limit so that it is larger than post_max_size.