Don’t print any debug info into the page directly. WordPress offers a wp-content/debug.log file which you can use.
Enable debug and debug_log in your wp-config.php
define( 'WP_DEBUG', true ); // turn debug mode on
define( 'WP_DEBUG_DISPLAY', false ); // do not display errors
define( 'WP_DEBUG_LOG', true ); // save errors to wp-content/debug.log
define( 'SAVEQUERIES', true ); // save queries for debug
Add this handy function to your functions.php or plugin file
/**
* Simple debug trace to wp-content/debug.log
* @usage _log( $var );
*/
if ( ! function_exists( '_log' ) ) {
function _log( $log ) {
if ( true !== WP_DEBUG ) {
return;
}
if ( is_array( $log ) || is_object( $log ) ) {
error_log( print_r( $log, true ) );
} else {
error_log( $log );
}
}
}
Use it in your code whenever you need to print some debug info
_log( $my_var );
Open wp-content/debug.log and see you data printed there. I usually keep it as a pinned file in my IDE (PHPStorm).