call_user_func | A benchmark study of call_user_func | Machine Learning library

Based on your question this are the explanations of the values.

$validator->failed(); is the answer.

It contains all failed rules:

The API seems to be working consistently the day after, so I'm assuming that laravel and/or AWS has some sort of dynamic throttle whose threshold was lowered due to low traffic as a result of our prior API issue. Always better to have issues that fix themselves!

If you made the call with call_user_func(array ($this, $this->InputHandler)); a method name is expected as the 2nd array element.

The error is specifically calling out line 35 of helpers.php:

You basically need to extend the Validator to make changes on that method and then make your own Validation Factory to create this new Validator instead of the default one. So step one with you own validator:

As shown below, I solved it by changing the validator so that it works only when the parameter is acquired by isset.

The reason why you are getting that warning is already mentioned in comments section by @LoicTheAztec. I will quote his comment here:

That is when a hooked function name doesn't match with the hook association… so for example when you have add_action('hook_name', 'function_name' ); and so function_name doesn't match with any declared function… This can happen when renaming a function, but not renaming the function name in the hook association.

I will give some pointers on how to debug and resolve the issue. Since you mentioned that it happened all of a sudden and you have not done anything, I assume that it might be caused by a plugin. One of your plugin might be updated and the plugin developer might have made this mistake.

What you can do is, visit your WordPress Admin Dashboard --> Plugins page. Then deactivate each plugin one by one. Make sure you check after deactivating each plugin, so that you would be able to figure out which plugin is causing the issue. While you are deactivating the plugins, if the warning disappeared, you would be able to tell that the plugin that you just deactivated is the villain here.

Since you figured out the plugin causing the issue, check whether it has any updates available. If so, update that plugin and see if it resolves the issue. If no updates,

1. you could try contacting the plugin developer, reporting the bug.
2. or, you could try debugging and fixing the bug yourself (if you are comfortable with coding)

If you plan to fix it yourself (#2), then try looking at the sourcecode of the plugin. Location would be : /wp-content/plugins/name_of_plugin

You can use the File Manager in your cPanel or use FTP, to access the files. On each file of that plugin, you have to search for add_action(. And note down the second parameter, which would be callback function name. And search whether that function is defined somewhere. If not defined, then it could be mispelled. You have to find the mispelled function definition and change it's name to what is being used (as second parameter) of add_action()

This will resolve the issue. In other case, while you are deactivating the plugins one by one and the warning message never disappeared even after trying to deactivate all the plugins, then you need look at your theme files (location: /wp-content/themes/your_current_theme_name_here/ )

To search for the keywords within files, there's a good plugin called String Locator. I most often use it for debugging purposes. Might come in handy for you.

According to your composer.json, you are using zircote/swagger-php in v3. The code you are using looks like something that is not compatible with v3, as the maintainers changed their namespace from Swagger to OpenApi

You either need to follow a tutorial that is made for v3, or downgrade the package you are using to v2