I created a small plugin to test database interactions in wordpress. I have a small function that inputs the arguments to the table.

If i call my function in a themefile it inputs my test values to my table, but if i call it from another plugin i get this error:

Notice: ob_end_flush(): failed to send buffer of zlib output compression (0) in /.../wp-includes/functions.php on line 2504

I have no idea what this error means, can anyone shed some light on it?

edit: I use MAMP with PHP 5.4.4


function test_db_function($name, $message){
  global $wpdb;
  $table_name = $wpdb->prefix . "testDB";

  if( $name == '' || $message == '' || !isset($name) || !isset($message)) {
    //return 0;
    $rows_affected = $wpdb->insert( $table_name, array( 
      'time' => time(), 
      'name' => $name, 
      'text' => $message) );

1 Answer 1


You did not provide that information, so I have to guess a little bit: You are using PHP 5.4 and zlib.output_compression is on on your server?

Then you just stumbled upon bug #18525. Possible solutions:

  • Disable zlib.output_compression.
  • Apply the patch provided there and report back on that ticket if it works.
  • Disable notices.

What you can do when you decide to release the plugin to the public is another issue …

  • Thank you for a quick response, realized i provided a little information. I use PHP 5.4.4 in MAMP.
    – andeersg
    Oct 26, 2012 at 19:57
  • I see that bug happens on auto-updates of plugins. I get the notice when calling a function from my plugin, and the function is not performed.
    – andeersg
    Oct 26, 2012 at 20:07
  • 1
    Same problem here - I found that adding ini_set('zlib.output_handler', ''); at the top of my plugin solved it.
    – adam
    Jun 4, 2013 at 20:12

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