Http error 500 php iis

500 internal server error clearly indicates that something went wrong during the display of PHP page.

By default, web servers like IIS return only generic error messages in websites. Often, this causes the masking of real reason for IIS PHP errors such as 500 internal server error.

That’s why, we frequently get request from Windows server owners to find out the reason for PHP website errors and fix them as part of our Server Management Services.

Today, we’ll take a look on how Bobcares’ Engineers track the real reason and fix php 500 internal server error in IIS.

What causes PHP 500 internal server error in IIS

Basically, 500 Internal Server Error is IIS web server’s way of saying, “Something has gone wrong when I tried to display the page. Not sure what.”

Now, its time to see the exact reasons for the 500 errors.

1. Permissions Error

From our experience in managing servers, our Windows Experts often see PHP 500 internal server errors due to wrong permissions and ownership on website files. In Windows servers, every file and every folder has its own set of permissions. Again, some permissions are inherited from the parent folders too. And, when the PHP binary do not have enough permissions to execute the scripts, it can result in 500 internal server error.

Similarly, ownership of the files also create problems. In Windows, specific users like IIS User, IIS WP User, etc. should have access on the website folders and files. For example, the IUSR account should have modify permissions on php scripts. And, when there are permission problems, website shows PHP errors.

2. Bad PHP Settings

Yet another reason for PHP internal server error is bad PHP settings. The PHP settings are specified in the configuration file at C:PHPPHP.ini. PHP binary take the values from this file while executing scripts.

A classic example will be PHP timeout settings. When the website PHP scripts has to fetch results from external resources, PHP timeout values often cause trouble.  Most system administrators set timeout values in PHP to avoid abuse of the server resources. And, if the PHP script executes for a time longer than the threshold limits, it eventually results in 500 error.

3. PHP module errors

A very few 500 errors happen when the PHP module on the server as such becomes corrupt too. As a result, it results in processing failure of PHP scripts.

Luckily, when the website reports the 500 error due to module failures, IIS often show a more specific error messages like:

500.0 Module or ISAPI error occurred.
500.21 Module not recognized.

How we fixed PHP 500 internal server error in IIS

Fixing PHP 500 internal server error in IIS need a series of steps. Let’s now see how our Dedicated Engineers fixed it for one of our customers and made PHP scripts running.

The customer reported 500 internal server error on WordPress website running in IIS.

1. Turning On Display errors

While the error correctly suggested that PHP had caused 500 error code, it did not provide application-specific information about what caused the error. Therefore, the the first step of investigation was to turn ON display errors option. For this, our Dedicated Engineers followed the steps below.

1. Using Windows® Explorer, browse to C:PHP and open the Php.ini file in the PHP installation directory.
2. Edit and set the display_errors = On directive.
3. Save the file.
4. Reset IIS using the command iisreset.exe

After turning on the errors, we reloaded the PHP and it showed a PHP parse error:

Parse error: parse error in C:inetpubusersxxxhttpdocsmysiteerror.php on line 3 >>

Often browser settings only show friendly error messages. In such cases, we recommend customer to turn it Off. For example, in Internet Explorer Go to Tools, Internet Options, Advanced tab, and then clear the Show friendly HTTP error messages check box.

Thus, it was a coding error on the PHP script. We suggested script modifications to customer and that fixed the error.

2. Running PHP script locally

Yet another way to find the exact error is to run the problem php script within the server. For this, our Support Engineers connect to the server via rdesktop and execute php script using the php.exe binary. It would show the  DLL’s that are having conflicts and causing the 500 error. We fix these conflicts and make the script working again.

3. Correcting PHP settings

In some cases, we need to correct the PHP settings to get the problem solved. Recently, when a customer reported problems with his website, we had to set the php directive open_basedir correctly to solve 500 Internal Server Error.

Similarly, when PHP cgi scripts show up some warning, IIS7 still displays an HTTP 500 error message. Although the best method is to fix the PHP scripts, often changing the default error handling for FastCGI in IIS7 to “IgnoreAndReturn200” also work as a temporary fix. The exact settings will look as shown.

4. Fixing PHP binary

In some rare cases, the fix may involve complete rebuilding of PHP binary on the server. This happens mainly when the PHP program on the server becomes corrupt. However, in such cases our Dedicated Engineers always check the dependency of the package and do the reinstall. For control panel specific servers, we set the appropriate binary on the server.

[Broken PHP scripts causing big problems? Our IIS experts have the fix for you.]

Conclusion

In a nutshell, PHP 500 internal server error in IIS happens mainly due to reasons like buggy PHP scripts, wrong server settings and many more. Today, we saw the top reasons for the error and how our Support Engineers fix it for customers.

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Resolve the 500 Internal Server Error for PHP 7.4 with IIS on Windows Server for WordPress

Many of my readers will know I run a tight ship when it comes to keeping my blog infrastructure up to date and as secure as I can. This means, among other things, I keep my operating system recent and patched. The same goes for my MySQL database, PHP versions, and WordPress + plugins.

Recently I wanted to upgrade to PHP 7.4 that was just released and should be compatible with WordPress 5.3.1.

But once I switched to PHP 7.4 my site responded with the dreaded 500 Internal Server Error. Instead of going trial and error I decided to zoom in fast to the root cause to resolve the 500 Internal Server Error for PHP 7.4 with IIS on Windows Server.

Troubleshooting steps

The fasted way to figure out what issues PHP has is to open an elevated command prompt and navigate to the install path of your PHP version. For me, that would be C:Program FilesPHPphp-7.4.0-nts-Win32-vc15-x64. Note that IIS with requires the non thread safe version of PHP.

Once there run php -m

I got greeted by this warning.

PHP Warning: ‘vcruntime140.dll’ 14.0 is not compatible with this PHP build linked with 14.16 in Unknown on line 0

That ‘s clear enough. I need to upgrade my Visual C++ runtime. I have but I need a more recent version. Basically the one for Visual ++ 2105-2019. You can grab those here for both x64 and x86.

https://aka.ms/vs/16/release/VC_redist.x64.exe
https://aka.ms/vs/16/release/VC_redist.x86.exe

I tend to install both. Just in case I have an issue with x64 PHP I can try the x86 version to try and resolve it, Normally I default to x64 bit and for the past years that has worked very well.

Once I had installed those my blog sprung back to life and that was it. If you run php -m again you won’t see the warning anymore. No need to switch themes (I have a simple one that has longevity). I also do not have to empirically disable/enable plugins. I select quality, free and modern plugins that I keep up to date or replace when needed. So, for me, that was the fix. Since most troubleshooting guided don’t start here, give it a shot. The HTTP Error 500.0 – Internal Server Error is an annoying one to troubleshoot. The PHP error log might not tell you anything as it goes wrong before it can log anything and enabling more detailed error handling does not always pinpoint something precisely. It might even send you on a wild goose chase.

If you did change the feature settings for the error pages for your site to get more detailed information to “Detailed errors” don’t forget to set it back. Configure it back to the default of  “Detailed error for local requests and custom error pages for remote requests” or your custom pages. You don’t want the details shown publically.

That’s it. I hope it helps someone who tries to resolve the 500 Internal Server Error for PHP 7.4 with IIS on Windows Server

If your Internet Information Services (IIS) produces a 500 – Internal server error, your website is in serious trouble. Debugging an IIS 500 – Internal server error can take some time, so you’d better be prepared for the worst-case scenario. You don’t want to research how to deal with this error under time pressure.

In my previous posts, you learned about detailed errors and failed request tracing in IIS (Internet Information Server). I recommend reading those articles first before you proceed with this one.

Cause of 500 – Internal server error

This is the most common error you will encounter with any website hosted with IIS. In most cases, a developer messed up. Thus, the fastest way is often to simply reverse the last action taken, such as restoring an earlier version of your web application. Once your system is running again, you can investigate the cause of the error on your test side in peace.

The HTTP 500 error is a server-side error. While we understand that the problem is on the server end, the error is usually ambiguous. It doesn’t exactly tell the administrator what is wrong with the server. Thus, debugging a 500 – Internal server error often takes some time.

Debugging an IIS 500 – Internal server error

Since the above error doesn’t really tell what’s actually wrong with the server, we need to enable detailed errors, as discussed in my previous post. Once detailed errors are enabled, you will see more detailed error information, including an HTTP substatus code. Sometimes even the detailed errors don’t show any useful information right away. For example, see the following screenshot:

Here I am getting: The page cannot be displayed because an internal server error has occurred. There is no HTTP status code or substatus code listed on the error page. If you get such an error even when detailed errors are enabled, right-click anywhere in the browser window and select Inspect (or press F12).

This opens the developer tools in your browser window. Now, click the Console tab. The actual error thrown by the web server is displayed.

To further understand the exact cause of 500 errors, enable Failed Request Tracing, as discussed in my previous post. Now, try to replicate the problem. If you can replicate it, open the newly generated XML log file in a web browser. The following screenshot shows the actual cause of a 500 – internal server error with a substatus code of 19 (HTTP 500.19 error):

Usually, substatus code 19 indicates that the configuration data is invalid. This could be due to some malformed or unidentified element in a server-level config file (ApplicationHost.config) or website-level config file (web.config). If you take a closer look at the ConfigExceptionInfo field of the log file, you will find the exact line number (6 in our case) in the web.config file that caused the exception. Now let’s take a look at the web.config file itself.

Here, you can see that the developer tried to add a mime type in the config file, but it was already defined in the server-level configuration file (i.e., ApplicationHost.config). Therefore, the Cannot add duplicate collection entry of type ‘mimeMap’ with unique key attribute ‘fileExtension’ set to ‘.mp4’ exception was returned. Furthermore, if there is some unidentified element, a syntax error, or even a typo in the web.config file, you will most likely get a similar error.

Resolving an IIS 500 – Internal server error

To resolve an IIS 500 – Internal server error, you could simply remove the line that is causing the exception. Alternatively, if you don’t want to remove this line for some reason, add the following code right above line 6 in web.config:

<remove fileExtension=".mp4" />

By doing this, you are essentially overriding the server-level element. In the end, your web.config file should look as shown below:

Now refresh the page, and the error should go away. This was just one example of resolving a 500.19 error. If you get a 500 error with a different substatus code, use the same approach to troubleshoot the problem.

Common 500.x substatus codes

The following table covers some of the most common HTTP 500 substatus codes, along with their probable causes and troubleshooting advice:

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Once you troubleshoot the problem, don’t forget to disable Failed Request Tracing and revert the detailed errors to custom errors on your web server.