External wpdb connections in different plugins on single page

You’ll have to make the variable global when you define it, e.g.

global $mydb;
$mydb = new wpdb('username','password','database','localhost');

and then use global $mydb; in the other plugins. Aside from theme files, functions.php, and plugins while being loaded, pretty much nothing in WP runs in global context, so if you need to access global variables, you’ll have to use global.

Related Posts:

  1. How to properly insert data into custom table via plugin
  2. How does WordPress handle MySQL row lock errors?
  3. Can I explicitly specify ENGINE=InnoDB in WordPress?
  4. Bad Request (Invalid Hostname) on working server, database problem
  5. Changing BIGINT to INT
  6. greatest() function returns undefined property
  7. How to write one comment and publish on every post using database or plugin?
  8. How to determine what is generating large amount of database queries?
  9. Help With MySQL to WPDB Query Conversion
  10. How can I perform high-level database merging for WordPress within continues delivery?
  11. WordPress Backend HA (Automatic failover)
  12. Automatic switch to backup database on fail
  13. Migrating to WordPress Recipe Plugin and Some SQL Issues
  14. Multiple instance of data in plugin custom database table on plugin activation
  15. Better ads plugin has 500.000 entries in wp_postmeta
  16. after wordpress update to 3.5+ i get many errors in plugin wpdb::prepare()
  17. dbDelta not adding additional columns in plugin database update
  18. Always get creating a new table with foreign key
  19. How to do database for download stats?
  20. DB Query not working in Plugin
  21. WordPress plugin: efficient way to store large data
  22. WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version [closed]
  23. Integrating Custom Database with WordPress
  24. How to display results from a data table with an encrypted user id?
  25. add_action for publish_post doesn’t work
  26. What database state changes happen after a post is manually “updated” with no changes?
  27. Cant create table on plugin activation
  28. Performing CRUD operations on front end in wordpress
  29. Store GravityForm data in phpmyadmin (mysql)
  30. Moving a few select DB tables to a new WP instance
  31. WordPress database problem wp_posts, primary key
  32. HyperDB failover Delay
  33. Write mysql credentials in plugin
  34. How can I delete the options from DB when the plugin is deleted?
  35. Is it bad practice to create own table for a plugin?
  36. Is there a plugin that will override the “Error establishing a database connection” message? [closed]
  37. What are these entries in the database? Looks similar to JSON
  38. How to empty wordpress custom post Database table
  39. insert data in database table from plugin with WP3.1
  40. $wpdb->get_results leaking memory
  41. Searching users with WP_List_Table plugin
  42. Is it a bad practice to go directly to the mysql database while developing a plugin?
  43. Custom database table for plugin not creating on activation
  44. Help!! I Screwed up my WP
  45. Should I global $wpdb outside of any of my plugin’s functions scope?
  46. How to edit/delete single row items in a table on my own menu page
  47. Unable to create new database table upon plugin activation using dbDelta
  48. mysqli_error() expects parameter 1 to be mysqli, null given in own db class
  49. Display data on Word Press site posts and pages from mysql table
  50. Plugin Options Not Saving to Database in WP 4.5
  51. Doubt using $wpbd->get_col for a single column
  52. Access WordPress database outside of WordPress
  53. WordPress Settings Lost After Site Migration
  54. join 2 table orders wordpress plugin
  55. How to remove traces from widget during uninstallation
  56. 306 MB of wp_options occupied by WordPress SEO Plugin, is that normal? [closed]
  57. how to access all user dashboard on fronted page [closed]
  58. import posts with dutch/special letters
  59. “Master” WordPress Multisite – Database Sync
  60. How to create multiple database tables on plugin activation?
  61. Does deleting a Plugin via the WordPress admin ‘completely’ remove the code?
  62. Cannot get wpdb data (Error in a simple fuction) [closed]
  63. Notice: Uninitialized string offset: 0 in social sharing mu-plugin
  64. Best/Correct way to add an option to a category
  65. Where do plugin variables live in the db?
  66. Way to send multiple values for column to MySQL?
  67. Plugin: connect to external database without showing password
  68. Storing Form data in a different database
  69. How to add a custom form to a plugin’s setting page
  70. update_option creates an option, which empties on a blog reload
  71. More than one WordPress site using the same database – how to disable plugin for one site?
  72. need to find duplicated meta value in custom filed and view the posts that have the same value
  73. My CPU usage in A2 Hosting Shared Plan (Turbo Boost) is high due to mysql query!
  74. Getting current user data with MySQL statement
  75. Memcaching recurring SQL Queries
  76. Can i stream data to a custom_post_type?
  77. How do I add a medium to the WordPress database with my own plugin?
  78. How to get database connection details without longing to cpanel in WordPress?
  79. Get Shortcode output to database for static post_content
  80. My wp database has been hacked
  81. How to update a database entry with a wordpress plugin?
  82. How can I store user preferences in WordPress and retreive them later?
  83. Enable plugins that are “not supported”
  84. one admin for 2 wordpress websites
  85. My plugin can’t see my files
  86. Resetting AUTO_INCREMENT primary key
  87. Need help for creating custom table on wordpress
  88. Show a table from data submitted by a form from a user
  89. Insert data in custom table during new post creation
  90. Managing database tables in WordPress multisite
  91. How to submit the custom form data in database in WordPress without plugin?
  92. Duplicator live to wamp https to http
  93. Is it possible to recover Deleted users?
  94. User register hook can’t access form request
  95. Post sorting and ordering function in WordPress Admin is broken and always shows post from oldest to newest
  96. PHP Creating a formula from mysql db values and db stored math operator
  97. Fragmented Static Conversion of WordPress Pages
  98. Getting 504 Gateway Timeout Error on AWS Server! [closed]
  99. WordPress issue – data is not showing in wp-admin, but when searching through database, all the data is there
  100. plugin doesn’t retrieve data from database