500 error indicates a server config issue…  could be running out of php memory or other… usually, something is put in the error log…

I had this issue yesterday and it had to do with the simple press avatars conflicting with wordpress/buddypress avatars. not sure if you are having the same issue. 

I don’t have buddypress. But the issue could be wordpress avatars. How did you fix it?

And is there any way to track down the source of the problem?

As it is right now, I’m looking at having to find another forum, and it took me ages to find this one, this does everything I need it to do (except, at the moment, work) and I invested significantly in order to use it.

I don’t want to go somewhere else. I simply want to get this to work.

The issue with Avatars is strictly to do with the BuddyPress plugin so has no relevance.

As Steve pointed out in the first reply above – you really do need to check the error log for a 500 server error. They almost always put the information in there regarding the cause and it really is the only place to go to find out what the situation is. It is quite obviously not a general problem or we would have no users! And as Steve also pointed out – 500 does mean a server error condition.

This is what the cause has been every time:

Premature end of script headers: plugin-editor.php, referer: http://mysite/ wp-admin/ plugins.php? activate=​true & plugin_status=all&paged=1&s=

Code split so you could see what it says.

Unfortunately, I have no clue what to do with this.

You get this on activation? After an FTP upload? What FTP client is this? Could it be corrupting the code? If FileZilla could you try a desktop client ftp application because FileZilla seems to corrupt any set of files over 2mg in total.

just to be clear (since its tagging along on a different topic regarding activating a plugin for simple press), this is activating the simple press plugin in the wp admin?   what it looks like from the message…

why is it needing activating?  thought you were using it?  or is this what you are getting on upgrade?  or is it really a new install?

As Andy says, have you verified the integrity of the upload? might be worth reuploading…

This is a fresh install.

I upload the plugin with FTP, using Transmit (a Mac FTP client, and usually very reliable).

I  click the activate button from the install plugin page.  

The plugin appears on my plugin page.

I click the activate button on the plugin page.

The plugin generates the 500 error.  

My web host ran the logs for me last night to make sure that was actually the error message generated by activating the plugin. It was.

They’re going to test the activation for me tonight after I’m done with my work, and see if they can figure out what’s going on.

If they find out anything, I’ll let you know tomorrow.

I need to note above that I wrote the first step twice above, but now can’t edit it. There was nothing twice. The activate was just once per attempt, followed by deleting the entire plugin so I could get my site to work again.

Okay, just to be sure, I downloaded a fresh copy of the plugin from the site, unzipped that, FTP’d it into my plugins folder, and clicked the activate link on the plugin page, and got the 500 error again. 

So my TigerTech guys will do their thing tonight, and I’ll let you know what they find out tomorrow.

Look forward to hearing the diagnosis…

Okay. Here’s what my Tigertech guys found:

As a followup to this: We’ve looked into it in detail.

When we first logged in, there wasn’t a deactivated “Simple:Press” plugin — perhaps you forgot to re-add it? — so we downloaded the demo one from their site and installed it.

After doing so, we did see intermittent 500 errors, as you said. These all left an extremely unusual error in the logs:

PHP crashed on opline 8 of classes() at /mysitepath/wp-content/themes/dejavu/framework.php:119

Some experimentation indicates that something about the SimplePress plugin causes PHP to crash when eAccelerator is enabled (and perhaps only when ionCube Loader is also enabled, based on some additional testing, although we couldn’t confirm that because we can’t fully disable ionCube Loader on [the site]).

This is the first eAccelerator/script incompatibility we’ve seen in some years, so we’re surprised by this. Some searching suggests that this can happen when software does many different levels of “require” and “include” in PHP, possibly because it’s running out of memory.

For most customers, we’d recommend switching to PHP 5.4, which contains
updated versions of both ionCube and eAccelerator, and our guess is that it would probably solve it. However, in your case, you have a very fragile mixture of PHP versions already running, and we’re reluctant to touch it, which means that the safest thing to do is switch off eAccelerator, at least for now.

Doing so appears to have solved the problem. We’ve left the Simple:Press plugin enabled, but we no longer see any 500 errors. Let us know if you agree that it’s solved.

Disabling eAccelerator will make the site slightly slower, though. You’ll need to test it and decide whether it’s still okay. (We didn’t notice it feeling slower after we made the change, but we don’t really have a feel for the “normal” speed of it.)

If you ever stop using this plugin, or when you can eventually upgrade to PHP 5.4 or later (we’ll soon make version 5.5 available), you should re-enable eAccelerator in our “My Account” control panel and see if it works — we guess it will.

Please let us know if there is anything else we can do. Thank you again!

—
Robert Mathews, Tiger Technologies

Fascinating…. I don’t know which version of php you on of course but one of them – and I think it was php 5.2 – was notoriously flaky and is not recommended t be used on a live site. Although it might have been a sub-version of that.

It’s good of your host to do so much in the way of diagnostics. Do you plan on accepting their advice?

It’s one of the subversions—but I’m stuck there because I’m using one-off software that can’t be upgraded.

Yellow Swordfish said
Fascinating…. I don’t know which version of php you on of course but one of them – and I think it was php 5.2 – was notoriously flaky and is not recommended t be used on a live site. Although it might have been a sub-version of that.

It’s good of your host to do so much in the way of diagnostics. Do you plan on accepting their advice?

Absolutely. I have the best host ever (after having spent years with many that were pretty bad). And the dev site I’m building does not have the php-version-dependent weaknesses of my live site. The second we get this sucker live, they’ll bump me up to the current version of php.

Hopefully Living without the accelerator extension for a while will get you past the hump…
I ought to look up which 5.2.x it was that was, er, untrustworthy shall we say…