automatic activate a plugin after install

automatic_activate_plugin.php

add_filter( 'upgrader_post_install', 'autoactivate_plugin_after_install', 10, 3 );

function autoactivate_plugin_after_install( $value, $hook_extra, $result ){
$p_tmp = get_plugins('/' . $result['destination_name']);
$p_key = array_keys( $p_tmp );

$pre = ! empty( $result['destination_name'] ) ? $result['destination_name'] . '/' : '';

$plugin = $pre . $p_key[0];
$plugins = get_option('active_plugins');

if( ! in_array( $plugin, $plugins ) ){
array_push( $plugins, $plugin );
update_option( 'active_plugins', $plugins );
echo __('Plugin erfolgreich aktiviert');
} else {
echo __('Plugin konnte nicht aktiviert werden');
}

unset( $p_tmp, $p_key, $pre, $plugin, $plugins );

return $result;
}