wp_write_log_helper.php

<?php
/**
 * Debug helper, place near the top of your functions.php
 * Use with write_log($var) to write $var contents into debug.log
 */
function write_log( $data ) {
    if ( true === WP_DEBUG ) {
        if ( is_array( $data ) || is_object( $data ) ) {
            error_log( print_r( $data, true ) );
        } else {
            error_log( $data );
        }
    }
}