Display custom debug info inside page and not before head

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).

Related Posts:

  1. How to hook update_post_meta and delete_post_meta?
  2. Are there any hooks that alter the 404 logic?
  3. WooCommerce: change display order of product short description and price [closed]
  4. Add_action to wp_head via functions.php
  5. Is there a WordPress core & plugins update action hook?
  6. trigger save_post event programmatically
  7. Implementing advanced add_* function wrappers
  8. My add_action (wp_footer, ‘method’) is not calling?
  9. Hook into wp_head(); in a plugin
  10. is it possible to get the hook name in add_action?
  11. What hook is executed just after wp_query has been executed?
  12. How can I hook into the post editor title field in order to change the HTML?
  13. How to properly test a method that is called by an action hook
  14. How can I do customizations on login, registration and password recovery forms?
  15. WordPress v5.0.3 Gutenberg & JS error “Uncaught SyntaxError: missing ) after argument list”
  16. Can’t get ID of post that relates to the comment
  17. Searching hook to set cookies before and avoid “headers already sent”
  18. Custom form action hook
  19. How to send an automated user ‘inactivity’ email?
  20. wp_redirect() not working on form submission with init hook
  21. How do I successfully create a hook for an email override?
  22. WooCommerce – Overwrite action hook [closed]
  23. Cast string to number
  24. How to debug user_register hook
  25. Storing state between hook functions
  26. Using wp_editor tinyMCE in metabox cause form alert on leaving page
  27. What’s the difference between “wp” and “wp_loaded”?
  28. WordPress capabilities and restricted categories access
  29. Hook when new CPT published AND postmeta inserted
  30. When WP_CLI runs WordPress from the command line, are hooks called?
  31. Query categories that have a description
  32. How to use custom form on add_meta_boxes callback
  33. Is it possible to switch Gutenberg’s editor styles when document settings change?
  34. schedule event in class oriented plugin
  35. How can I find the hook I need to rewrite a function?
  36. Show message in media-new.php
  37. Hooks are not being removed in child theme
  38. add_action second argument missing
  39. How to get user meta fields that have just been updated?
  40. admin_notices action doesn’t trigger within save_post action
  41. When a plugin gets updated from the repo, does the “activation” hook fire again?
  42. I don’t understand how add_action and do_action work in tandem. The former executes the code already…what is do_action for?
  43. Insert HTML in post, below nav bar but above content?
  44. Convert Gravity Form Entry Date on Export
  45. Hook Adding content after title
  46. Fatal error: Call to a member function get_queried_object_id()
  47. Defining hooks within (php)classes?
  48. Divi hook not working [closed]
  49. Add WordPress hook outside of Plugin or Theme
  50. How to add content to suscriptor dashboard frontend?
  51. How to perform action when plugin/theme editor is used?
  52. Add PHP code to header section from plugin
  53. How to run hooks one by one manually?
  54. What is the proper hook to use for recording a post view?
  55. How to load this code on function.php
  56. What hook should I use that will fire whenever I open a post for editing in the WP back-end?
  57. Woocommerce single_product_summary hook not working
  58. Where is publish_post hook fired?
  59. A good hook to check authorization and redirect?
  60. Is there a author_update action?
  61. Bloginfo hook – can it be more precise?
  62. Custom posts and get_post_meta in {$post_status}_{$post_type}
  63. Hooking custom PHP output into WP: how to do it, parse_request almost works but not quite
  64. Print on screen during shutdown hook – error during saving in theme-editor.php
  65. How to stop execution of a function via add_action hook?
  66. changing genesis_before_while in new theme framework
  67. Moving Javascript from footer to header
  68. Adding a new hidden field based on a condition in Ninja Forms
  69. Forcing WooCommerce customers to create account before checking out
  70. Store user ID on wp_term_taxonomy when new term inserted
  71. ‘user_register’ hook – need to distinguish if created from wp admin panel
  72. Make multiple URLs behave as home page
  73. remove_action not working for a function
  74. Debug a WP install: how to find which functions write post updates during a process (a woocommerce checkout in my case)
  75. What hook should I use to add post meta data with on update?
  76. Transition_Post_Status hook not working properly
  77. Wodpress XML Import hooks
  78. profile_update hook does not fire from front-end
  79. wp_update_post not getting triggered by hook
  80. How to get user profile information before update?
  81. Why is pre_get_posts hook invoked multiple times?
  82. Undefined fieldId in gform.addFilter for limiting dates in datepicker – Gravity Forms
  83. Get First Post content and edit it using pre_get_posts (or similar?!)
  84. Are there Hooks for featured image popup?
  85. Change user role if it’s orders count more than
  86. Exclude WooCommerce terminations from YOAST
  87. set_post_format called after wp_update_post when using bulk edit?
  88. add hook restricted only to either plugins or themes?
  89. How to hook watchdog script for existence of a WP page?
  90. Using actions, hooks and filters in a non-WordPress page
  91. Hook into create_category
  92. Trouble adding data to options table
  93. How to hook into publish_posttype?
  94. How to add a new link to the default register form’s footer links?
  95. $GLOBALS & global doesn’t work [closed]
  96. Hooks not working on live server
  97. Use wordpress search hooks to search a second database
  98. Why callback function is not working in wp_head hook?
  99. woocommerce_add_to_cart_validation max quantity depending on user geoip [closed]
  100. theme.json is altering Group block HTML
Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)