As Plesk overwrites the php.ini for the Apache webserver, you have to create a file vhost.conf inside the webuser's directory in the folder conf with the following content:
DocumentRoot /var/www/vhosts/meinedomain.com/httpdocs/web
<Directory /var/www/vhosts/meinedomain.com/httpdocs/web>
<IfModule mod_php5.c>
php_value memory_limit 512M
php_admin_value open_basedir "/var/www/vhosts/meinedomain.com/httpdocs:/tmp:/usr/bin:/usr/local/bin"
php_admin_value post_max_size 1024M
php_admin_value upload_max_filesize 1024M
php_admin_value safe_mode Off
php_admin_value register_argc_argv On
php_admin_value register_globals Off
</IfModule>
<IfModule sapi_apache2.c>
php_value memory_limit 512M
php_admin_value open_basedir "/var/www/vhosts/meinedomain.com/httpdocs:/tmp:/usr/bin:/usr/local/bin"
php_admin_value post_max_size 1024M
php_admin_value upload_max_filesize 1024M
php_admin_value safe_mode Off
php_admin_value register_argc_argv On
php_admin_value register_globals Off
</IfModule>
</Directory>
Next Plesk has to be informed to import the modifications. This can be done with the following command:
/usr/local/psa/admin/sbin/websrvmng --reconfigure-vhost --vhost-name=MEINEDOMAIN.TLD
On Ubuntu:
/opt/psa/admin/bin/websrvmng --reconfigure-vhost --vhost-name=MEINEDOMAIN.TLD
The vhost.conf configuration only works for the Apache Webserver. For the php-cli the values have to be entered into the according php.ini additionally.