Logging system in PHP framework

　

Now I am working as a PHP backend development programmer in a company (our team does not have a front-end, so we will do front-end things when doing activities). When I first came to the company, I spent 2 weeks to run a front-end plus back-end activity (I remember at that time I couldn’t do it, so I had to work overtime for two days on the weekend...,,,). It’s been more than 4 months now, and I can finish a not very complicated activity in one afternoon. Of course, when I do it now, I will consider many things, such as expansion. flexibility and reusability, because if you do more, you will accumulate a lot of things similar to small plug-ins, so it will be fast. . . . . . But I found that "standing in the requirements and doing the requirements" all day long is very poor. In this way, you will not learn system and framework things, because you are trapped by trivial requirements and have no time to do some important parts of the framework. , and when your colleagues and boss are used to you doing those things, they will push it to you without hesitation every time they encounter something that has no technical content but has to be done (to be selfish, everyone Programmers are all like me, they all want to master something with technical content, so that they can have a sense of pride as a programmer), and over time you will get used to it... This is really miserable, so I will take it out Take some time to learn the things in the framework and try not to be a simple coder.

^Quote

Friends who have come into contact with the PHP framework may know the important role of logs in the project. It can help us locate the location of the error and make the program more friendly (if handled properly, it will not directly throw out a lot of errors only for programmers) It is really moving in English), it will be very convenient during debugging, and it can also record some important operations, etc. In short, if a complete project does not have a log system, the development road will be full of thorns and potholes. It will definitely It's going to be stumbling.

Introduction

To master the PHP logging system, you must first have a thorough understanding of these things.

1. Several functions of php

1 set_exception_handler(callback $exception_handler); //Exception capture custom handler function registration

1 set_error_handler(callback $error_handler); //Error capture custom handler function registration

1 register_shutdown_function(callback $callback); //Abnormal termination error capture handler function registration during program execution

These three functions provide developers with a lot of autonomy in error handling control, and they are responsible for recording log information in the log system.

When an exception occurs in the program, the php kernel will throw an exception error and then print the error message to the user. If an exception handling function is registered, the exception thrown by php will be transferred to the custom registered one. Exception catching function, this function contains the processing we need to do and records the error information (including error details and error location). After the function handles the exception, the exception will terminate.

When an error occurs in the program, the error handling function we registered will convert the error information into an error exception object in the function and pass it to the exception handling function, which is the $exception_handler function in the first step.

When a shutdown error occurs during the resumption, the abnormal termination processing function we registered will be executed. This function obtains the error object during the last shutdown through error_get_last(), and then generates an error exception object like the previous part, and This object is passed to our registered exception handler function.

It can be seen that in fact, whether it is an exception or an error, it converts its own information into the exception information recognized by the exception handling function, and then hands it to the exception handling function for processing. The non-exception information is like a woman with makeup, exception The handler does not recognize these non-exception information. Only when the non-exception information is loaded and unloaded (the non-exception information itself is converted into exception information, to be precise, it should be thrown), can the exception handler recognize it.

Error handling process in php log system

So now comes the question. These functions usually work with an exception handling library and an error logging library. The exception handling library contains 3 functions to be registered and a logging library. Called in $exception_handler, it is used to record and place the log file reasonably. The functions mentioned above are generally loaded and registered at the entrance of the program framework, like the following:

The array(class,function) method is used here.

<span>1</span> <span>set_exception_handler</span>(<span>array</span>("Myexception","exceptionHandler"<span>));
</span><span>2</span> <span>set_error_handler</span>(<span>array</span>("Myexception","errorHandler"<span>));
</span><span>3</span> <span>register_shutdown_function</span>(<span>array</span>("Myexception","shutdownHandler"));

2. Logging related libraries

The things introduced in the first part only capture exceptions, errors, and shutdowns. This is only the first step. Next, the captured information must be properly processed, such as recording the log information to the local file system. (This operation is in array("Myexception", "exceptionHandler")), where the logging class library is used. (The class library mentioned below draws on the design of the kohana log system).

Japanese-style logging is also very simple. All you need to do is add the information to the end of the file. This is easy to implement. I believe everyone can implement it by themselves, but it is necessary to design a convenient, efficient, and extended logging class library. It’s not that simple. It requires long-term practice, summary and optimization. The logging library in the kohana framework is relatively mature, so we can use it here for reference.

I believe that users who have used kohana must be familiar with the logging in the kohana framework. It doesn’t matter if you are not familiar with it. I will briefly talk about it below, No. 109 in the application/bootstrap.php file in the kohana source code—— You can see the following code at line 112:

<span>109</span> <span>/*</span><span>*
</span><span>110</span> <span> * Attach the file write to logging. Multiple writers are supported.
</span><span>111</span>  <span>*/</span>
<span>112</span> Kohana::<span>$log</span>->attach(<span>new</span> Log_File(APPPATH.'logs'));

This is to add a logging object to the log object. Pay attention to the two with olive color background. They are different class library instances. In kohana, the logging object is divided into two parts. The first part is The log object is used to maintain a list of logging objects. How to understand this? It is actually like a container, which contains one or more logging objects (this is the second part. These logging objects are the real source of the log object). Logging), and an array of error levels to be recorded for each object. When the error level is met, it will be recorded. If not, it will be omitted. Here is my own simplified logging method after renaming:

<span>1</span> self::<span>$log</span> = <span>Log</span>::<span>instance();
</span><span>2</span> self::<span>$log</span>->attach(<span>new</span> Logwriter("./data/debug"),<span>Log</span>::<span>DEBUG);
</span><span>3</span> self::<span>$log</span>->attach(<span>new</span> Logwriter("./data/notice"),<span>Log</span>::NOTICE);

In order to better understand here, I named the "container" as Log and the recorded instance as Logwriter. You can see that I easily added two different log types at the program entrance. The first one is to record all Errors with error numbers smaller than Log::DEBUG (error levels higher than him) are recorded under the folder ./data/debug according to rules. The second one is errors with a recording level equal to or higher than Log::NOTICE. Of course You can also specify which errors are good in more detail. Just pass the array. This is what I think is convenient and fast. We can add error logs and divide them into different log directories according to needs. Look at the picture below. Helps to understand:

The relationship between log and logwriter

You will see from the picture above that Log is a container that contains different specific logwriter objects. Each object may record different information. When the error information is written to the file, each Logwriter will be run. For example, see if you want to record the error in error message. If the level in error message is not included in Logwriter, it will be ignored.

How does this part cooperate with the first part? In fact, it is very simple. When an exception is caught by exception, it will be called to add an error message (including error location, error code, error message, etc.) to the errormessage array in the Log container, and then write this information to the file after the program ends. , please note here, maybe when you read the kohana code, you find that there is no obvious direct writing to the log. Kohana is better optimized here, because multiple errors may occur in one execution of php. If an error occurs, you Just record it once, which will take up extra IO and time before the program returns, so kohana's approach is to store all errors, exceptions, and logs in Log::$errormessage by default, and talk about the Log in it when instantiating it. The writer operation registers register_shutdown_function. The function of this function is to execute it after the program terminates abnormally or the execution is completed. It is also used in the first part above, so that the log record will not have a big impact on the execution of this PHP.

3. Example summary

At this point you should have an overview of the log system, and you can already write a "log system" for use. Let's take a look at the example of my "log system". This is the github address, which contains code and examples. You can take a look if you need to.

https://github.com/AizuYan/phplog.git

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The above has introduced the logging system in the PHP framework, including aspects of it. I hope it will be helpful to friends who are interested in PHP tutorials.