We've got a 4.6.10 CiviCRM site which has been running without fuss for a while. Now, when adding an event participant, we get an error 500. The process of adding the participant works fine (they appear in the list of participants) but the receipt does not get sent out and the page never returns. In the Apache error log, I see the following :

Allowed memory size of 536870912 bytes exhausted (tried to allocate 474218496 bytes) in /var/www/html/sites/all/modules/civicrm/CRM/Core/Error.php on line 550

The memory limit was actually 128M but it was increased, just in case. As you might guess, it makes no difference. I decided to set "display_errors = 1" in my php.ini, but that just gives me a completely white screen without the 500 error displayed.

Any thoughts or ideas on how to figure this one out would be greatly appreciated.

-- Marcel

1 Answer 1


It might be that the pdf receipt format is too complex, try to disable sending them, see if it makes a difference

It's under admin > setting > misc

"Attach PDF copy to receipts"

If you need to send the pdf, I recommend you to let civi use a dedicated software to generate the pdf instead of the default (doing it in php, that uses tons of memory), it's a setting in the same page: "Path to wkhtmltopdf executable"

you'll need to install this software on your server.

  • Interesting thought, Xavier. After posting this, I decided to try 'not' sending a confirmation receipt in email, and it worked perfectly. It's not the registration that's the problem, but the email that gets sent. I'm going to test out the PDF idea now. Commented Jan 22, 2016 at 17:28
  • Well, dang, Xavier! That was the problem. I will soon find out if the client likes that answer and whether they think a PDF copy of the receipt it somehow necessary, but at least it works again. If it's important, I'll look at wkhtmltopdf and install that. Commented Jan 22, 2016 at 17:34

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