WordPress: Clear PHP opcode caches before updates are applied, ease the updating process (https://www.saotn.org/wordpress-plugin-flush-php-opcache/)

clear-opcode-caches.php

<?php
/**
 * Plugin Name: Clear PHP opcode caches
 * Plugin URI: https://www.saotn.org/wordpress-plugin-flush-php-opcache/
 * Donate URI: https://www.paypal.me/jreilink
 * Description: Purges various PHP opcode and user caches. Currently it tries to clear / purge / flush PHP OPcache and WinCache caches from your web server's memory. This should ease WordPress updates and plugin activation / deactivation.
 * Network: True
 * Version: 1.2
 * Author: Jan Reilink
 * Author URI: https://www.saotn.org
 * License: GPLv2
 */

require_once( ABSPATH .'/wp-config.php' );

function clear_memcached_cache() {
	global $memcached_servers;
	if( isset($memcached_servers) ) {
		list( $socket, $port ) = explode( ":", $memcached_servers["default"][0] );
		$m = new Memcached();
		// $m->addServer( '/path/to/my/wordpress-site/temp/memcached.sock', 0 );
		$m->addServer( $socket, $port);
		if ( false === $m->flush() ) {
			return false;
		}
		else {
			return true;
		}
	}
}

function clear_iis_wincache() {
	if( ! function_exists( 'wincache_ucache_get' ) ) {
		return;
	}
	if( ! wincache_ucache_clear() ) {
		return false;
	}
	else {
		return true;
	}
}

function clear_php_opcache() {
	if( ! extension_loaded( 'Zend OPcache' ) ) {
		return;
	}
	$opcache_status = opcache_get_status();
	if( false === $opcache_status["opcache_enabled"] ) {
		error_log( 'extension loaded but OPcache not enabled' );
		return;
	}
	if( ! opcache_reset() ) { 
		return false;
	}
	else {
		/**
		 * opcache_reset() is performed, now try to clear the 
		 * file cache.
		 * Please note: http://stackoverflow.com/a/23587079/1297898
		 *	"Opcache does not evict invalid items from memory - they 
		 *	 stay there until the pool is full at which point the 
		 *	 memory is completely cleared"
		 */
		foreach( $opcache_status['scripts'] as $key => $data ) {
			$dirs[dirname( $key )][basename( $key )] = $data;
			opcache_invalidate( $data['full_path'] , $force = true );
		}
		return true;
	}
}

function is_iis() {
	$software = strtolower( $_SERVER["SERVER_SOFTWARE"] );
	if( false !== strpos( $software, "microsoft-iis" ) )
		return true;
	else
		return false;
}

function clear_caches() {
	if( is_iis() ) {
		if ( clear_iis_wincache() ) {
			error_log( 'WinCache user cache cleared.' );
		}
		else {
			error_log( 'Clearing WinCache user cache opcode cache failed.' );
		}
	}
	if( clear_memcached_cache() ) {
		error_log( 'Memcached flushed' );
	}
	if( clear_php_opcache() ) {
		error_log( 'PHP OPcache opcode cache cleared.' );
	}
	else {
		error_log( 'Clearing PHP OPcache opcode cache failed.' );
	}
}

add_filter( 'upgrader_pre_install', 'clear_caches', 10, 2 );

// cpoc = Clear PHP Opcode Caches
add_filter( 'plugin_row_meta', 'cpoc_plugin_row_meta', 10, 2 );
function cpoc_plugin_row_meta($links, $file) {
    if ( !preg_match('/clear-opcode-caches.php$/', $file ) ) {
      return $links;
    }
		
    $links[] = sprintf(
      '<a target="_blank" href="https://paypal.me/jreilink" title="Donate to Jan Reilink / Sysadmins of the North">%s</a>',
      __( 'Donate' )
    );
    return $links;
}

?>