Fatal error: Cannot redeclare class phpmailerException

[hovida]

All Plugins Disabled, all Themes disabled - Reinstalled - All the same error:

​http://www.tinnitus-coach.eu/wp-login.php?action=lostpassword

Fatal error: Cannot redeclare class phpmailerException in /homepages/23/d471228603/htdocs/wp-includes/class-phpmailer.php on line 2825

Same Problem when i use wp_mail on Cron shedules, see:
​http://wordpress.org/support/topic/wp-cronphp-wp_mail-not-working?replies=2#post-4626751

[SergeyBiryukov]

Could not reproduce the issue neither with the password reset form nor with your plugin from the forum topic, it works fine for me.

The only place in core where class-phpmailer.php in included is wp_mail(), but it first checks if $phpmailer global is defined, and it uses require_once rather than just require: tags/3.6/wp-includes/pluggable.php#L223​.

I can only reproduce this fatal error if I manually include class-phpmailer.php twice outside of wp_mail().

[chriscct7]

Closing as worksforme. Feel free to reopen if you can provide steps to reproduce

[pixelbath]

Was able to reproduce this problem using a global error handler that included its own phpMailer script. Pluggable.php does check if the $phpmailer global is defined, but not whether the base class exists (which would mean it's been included, but not initialized). Submitting a patch.

[pixelbath]

Patch to check whether the PHPMailer class exists prior to require_once

[desrosj]

As of WordPress 5.6, PHPMailer has been brought up to date with the upstream library (see #41750). Because this is the only report I can find for this error, I'm going to close this out as a wontfix.

Adding the extra safety check probably wouldn't hurt, but an external script loading its own version of PHPMailer could have other undesirable side effects. For example, if an older version of the library is loaded outside of WordPress and Core utilizes a newer feature within the library, that would potentially cause issues. Leaving this error could potentially help debug the issue so that improvements can be made.

If there are any factors being missed that should be considered, feel free to reopen this and add additional details.