Fatal error on upgrade to 5.3.2

@xnau: It looks like you need to clear your opcode cache (related to core ticket #36455). The easiest way is probably by restarting your PHP process (i.e. php-fpm).

Ah…right! Should have thought of that.

Do you happen to know how I can set it up so the cache is cleared when a plugin auto-update occurs?

I’m using this snippet in mu-plugins, taken from the discussion in the linked trac ticket:

<?php

/** 
 * Reset PHP opcache 
 * 
 * @since 4.8 
 * 
 * @return boolean 
 */ 
 function wp_opcache_reset($reply, $package, $wp_upgrader) { 
 	if ( function_exists( 'opcache_reset' ) && ini_get('opcache.validate_timestamps') != '1' && (!ini_get('opcache.restrict_api') || stripos(ABSPATH, ini_get('opcache.restrict_api')) === 0) ) { 
 		opcache_reset(); 
 		$opcache_status = opcache_get_status(); 

		if ( null !== $opcache_status && isset( $opcache_status['scripts'] ) ) {
 			$matches = preg_grep( "/^" . preg_quote(ABSPATH, '/') . "/" , array_keys($opcache_status['scripts']) ); 
 			if ( count( $matches ) > 0 ) { 
 				array_map('opcache_invalidate', $matches, array_fill(0, count($matches), TRUE)); 
			}
		}
 	} 
 	return $reply; 
 } 

add_filter( 'upgrader_pre_download', 'wp_opcache_reset', 10, 3 ); 

wow, thanks…it would have taken me hours to figure that out