What to do when searching for errors in php

PHP is a widely used programming language. It is widely used in the development of Web applications due to its easy to learn, easy to use, and powerful functions. However, some errors inevitably occur during the development process. How to find and solve these errors is a skill that every PHP programmer must master. This article will discuss common error types, tools and techniques to help PHP programmers locate various errors more accurately and efficiently.

1. Database connection error

MySQL is a database often used by PHP programmers, and database connection error is one of the most common PHP program errors. If a connection error occurs, the program will not be able to obtain data from the database, causing serious consequences. How to find and solve this error?

(1) Check database user permissions: First, make sure the database account has the correct permissions, such as SELECT, INSERT, DELETE, UPDATE permissions, etc. In web server software, such as Apache and Nginx, ensure that the database user has execution permissions in the server.

(2) Check the database connection parameters: Secondly, check the connection parameters to ensure that there are no errors in connection parameters such as user name, password, IP and port number. Similarly, make sure these parameters are correct in Apache and Nginx.

(3) Check the database server status: If there are no problems in the above two steps, it may be because the database server has not started or has stopped running. You can query the database server status through the command line or graphical tools to ensure that the database server is running.

2. Grammar errors

Grammar errors are one of the most basic knowledge points in programming languages, including missing semicolons, missing parentheses, non-existent variable names, etc. PHP does not have a compiler, which means there is no way to check the code for problems before executing it. When the PHP interpreter finds a problem when executing code, it will crash when this line of code is executed. As a result, an HTTP 500 error occurs, also known as "Internal Server Error".

(1) Use a code editor: Since syntax errors are difficult to locate, PHP provides various tools to check for syntax errors. Use a code editor, such as VSCode or PHPStorm, to display error messages as soon as code errors occur. In addition, you can also use PHP's own syntax checker command line tool or run the PHP syntax checker before code execution.

(2) Record PHP error log: If the error log is not recorded, syntax errors will be difficult to find. To enable PHP error logging, you can set it in the php.ini configuration file, which is usually located in /etc/php.ini on the server. In a development environment, error logging can also be enabled in PHP code: error_log(PHP_EOL.file_get_contents(__DIR__.'/error.log'), 3, __DIR__.'/error.log');

（ 3) Conduct regular code reviews: Whether it is a personal development project or team collaboration, regular code reviews should be mandatory. Code review will help find code that may cause syntax errors and reduce the occurrence of errors.

3. Runtime error

When an error occurs when PHP code is executed, such as dividing by zero, exceeding the memory limit, etc., a runtime error will occur. Such errors may cause the program to interrupt and exit, or even cause the server to crash.

(1) Use try-catch block: try-catch block can capture runtime errors and handle them. Exception handlers can be defined in the catch block, such as logging errors, providing feedback, retrying, etc.

(2) Optimize program quality: Experienced programmers reduce the incidence of runtime errors by focusing on performance, optimizing memory usage, modifying code logic and other operations.

(3) Check the PHP error log: Checking the PHP error log can help programmers locate the problem faster and solve the problem faster.

4. Namespace Error

Namespace is a mechanism that makes PHP code more readable and easier to maintain. A namespace wraps together a set of code consisting of functions, classes, interfaces, constants, etc., thereby logically classifying the code. But in order to achieve the correct namespace, you need to ensure that the class name, file name and namespace name match. If a wrong namespace reference occurs, you will get a "class does not exist" error.

(1) Ensure that the class name, file name and namespace name match: This problem can be solved by searching for the class name and namespace name. In an IDE or code editor, you can use the autocomplete feature or the import feature from an external code library to automatically fix namespace errors.

(2) Use standard namespaces: All PHP code should use standard namespaces, such as PSR-4. In addition, the naming of classes, methods, and properties should also follow the corresponding naming conventions, such as PSR-1 and PSR-12. This reduces code maintenance costs and makes the code easier to use and easier to read.

5. Type error

PHP is a loosely typed language, that is, the variable type is determined by the data type at the time of assignment. This mechanism makes it easier for developers to develop fast and flexible applications. But it also illustrates the effort that developers must make in terms of heavy data type conversions and taking the input and output of methods and operators seriously.

(1) Use data type checking functions: PHP provides many data type checking functions, such as is_numeric(), is_array() and is_string(), etc. Variable types can be checked when working with data to determine whether there are type errors.

(2) Use type strict mode: Change PHP's type strict mode from the default loose mode to strict mode, which specifies the data type of the variable and reduces the probability of type errors.

(3) Use IDE and code library: IDE and code library provide tools to detect type errors. Used in an IDE, similar to PHP Storm, you can perform automatic completion and code inspection on variable types, and detect type errors during development.

6. Logical errors

Logical errors refer to errors in the logic of the code, that is, the code does not operate as expected. Such errors can cause program interruptions, leave malicious holes and leak data, or even cause problems throughout the network.

(1) Write unit tests well: Unit tests are tests that test small, independent blocks of code. Since these blocks of code are small, they are easy to test. Unit testing checks whether the code performs as expected after writing it, and can test the practicality of the code when maintaining existing code. This helps reduce the likelihood of logic errors.

(2) Use popular coding standards: Popular coding standards (such as Pascal, C, Java, Ruby, etc.) describe some rules in coding style and conventions. Using these rules reduces the likelihood of logic errors and makes code easier to read and maintain.

(3) Conduct code review: During the code writing process or after the writing is completed, the team or individual should conduct a code review on the code. Code review includes an examination of code logic to find problems in the code.

Summary

The above are the common PHP error types and solutions. Troubleshooting is one of the basic abilities for every PHP programmer to create high-quality software. As long as you are proficient in error types and solutions, and accurately grasp the breakthrough point of troubleshooting, you can troubleshoot more quickly and accurately, making the PHP program run faster. Faster and more stable.

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