Knowledge Base

Different actions in WP Toolkit fail with the error: Argument #1 ($callback) must be a valid callback, array must have exactly two members

Symptoms

An attempt to update a plugin or log into WordPress Admin dashboard via Plesk fails with the error:

ERR [util_exec] proc_close() failed ['/opt/psa/admin/bin/filemng' 'example.com_t0p5ozstmoi' 'exec' '/var/www/vhosts/example.com/httpdocs' 'timeout' '60' '/opt/plesk/php/8.0/bin/php' '-d' 'safe_mode=off' '-d' 'display_errors=on' '-d' 'opcache.enable_cli=off' '-d' 'open_basedir=' '-d' 'error_reporting=341' '-d' 'max_execution_time=60' '-c' '/var/www/vhosts/system/example.com/etc/php.ini' '/opt/psa/admin/plib/modules/wp-toolkit/vendor/wp-cli/wpt-wp-cli.php' '--path=/var/www/vhosts/example.com/httpdocs' '--no-color' 'eval' 'echo wp_login_url();' '--skip-plugins=false' '--skip-themes=false'] with exit code [1]
PHP Fatal error: Uncaught TypeError: call_user_func(): Argument #1 ($callback) must be a valid callback, array must have exactly two members in /var/www/vhosts/example.com/httpdocs/wp-includes/rest-api/class-wp-rest-server.php:1487
Stack trace:
#0 /var/www/vhosts/example.com/httpdocs/wp-includes/rest-api/class-wp-rest-server.php(1428): WP_REST_Server->get_data_for_route()
#1 /var/www/vhosts/example.com/httpdocs/wp-includes/rest-api/class-wp-rest-server.php(1255): WP_REST_Server->get_data_for_routes()
#2 /var/www/vhosts/example.com/httpdocs/wp-includes/rest-api/class-wp-rest-server.php(1171): WP_REST_Server->get_index()
#3 /var/www/vhosts/example.com/httpdocs/wp-includes/rest-api/class-wp-rest-server.php(1018): WP_REST_Server->respond_to_request()
#4 /var/www/vhosts/example.com/httpdocs/wp-content/plugins/woocommerce/includes/cli/class-wc-cli-runner.php(63): WP_REST_Server->dispatch()