How to debug in WooCommerce 3+

As this is a background process on server side, don’t use javascript.

1). WC Logs and the WC_Logger Class in WooCommerce for better debugging

To access the results of the log easily from the dashboard, you can log to a WC logger rather than the error log.

You can access error logs by going to WooCommerce > System Status > Logs.

Then you will be able to choose and “view”the error log file you need, giving you the debugging details that you need. Error logs are also located in the /wc-logs folder within your site install.

Running a stack trace on a caught exception (example):

// Log any exceptions to a WC logger
$log = new WC_Logger();
$log_entry = print_r( $e, true );
$log_entry .= 'Exception Trace: ' . print_r( $e->getTraceAsString(), true );
$log->log( 'new-woocommerce-log-name', $log_entry );

Notes:

• WC_Logger methods have been updated since WooCommerce 3: So logging can be grouped by context and severity.

• Use WC_Logger log() method instead of add() method due to upcoming deprecation (thanks to @Vizz85).

For example:

$logger = wc_get_logger();
$logger->debug( 'debug message', array( 'source' => 'my-extension' ) );

Related:

• Develop WooCommerce blog (january 2017): Improved logging in WooCommerce 3
• Documentation on the WC_Logger available methods

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2). Debugging with WordPress WP_DEBUG Log (as an alternative)

a) First edit your wp-config.php file adding the following lines to enable debug (if these are already defined, edit the values):

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );

As errors are logged, they should appear in wp-content/debug.log. You can open this file in a text editor.

b) On your code: Use the following (where $variable is the variable to be displayed in the error log:

error_log( print_r( $variable, true ) );

Now you will get the data for debugging.