This plugin can log the breakpoints into the file.
tail -f /your_wordpress_path/wp-content/debug.log to watch the output.To log, use defined( 'debug' ) && debug( 'your content to log' ); in your plugin/theme code.
To log only in advanced debug level, use defined( 'debug' ) && debug2( 'your content to log' );.
To log with backtrace depth = 4, use defined( 'debug' ) && debug( 'your content to log', 4 );.
To append one variable (usually an array), use defined( 'debug' ) && debug( 'your content to log', $var_to_check );.