How to force output error message in php

During the development process of PHP, we often encounter various errors. Sometimes, these errors will cause our program to fail to run properly, requiring us to troubleshoot the errors. In order to quickly locate the problem, we need to force the system to output error messages.

In PHP, there are three common error output methods:

1. Use the echo or print function to output error information in PHP scripts.
2. Set the parameters of the error_reporting() function to control the error reporting level.
3. Set the error_reporting or display_errors parameters in the php.ini or .htaccess file.

These methods can control the output of error information, but in some cases (such as during debugging), we need to force the error information to be output to the screen. At this time we can use PHP The "set_error_handler()" function!

The "set_error_handler()" function is a function used to set a custom error handling function. Its prototype is as follows:

function set_error_handler (callable $error_handler_function, int $error_types = E_ALL | E_STRICT): mixed {}

Among them, $error_handler_function is the name of the custom error handling function. $error_types is a parameter that controls error types. By default, it prints all error messages.

The following is an example to illustrate how to use the "set_error_handler()" function:

function custom_error_handler($errno, $errstr, $errfile, $errline) {
    echo "<b>Error:</b> [$errno] $errstr<br>";
    echo " Error on line $errline in $errfile<br>";
}

set_error_handler("custom_error_handler");

Run this program. When an error occurs in the code, the custom_error_handler function will be automatically called to save the error message. Force output to the screen.

In this example, we implemented a simple custom error handler and defined a custom_error_handler function to force the error message to be output to the browser when a PHP error is captured.

Custom error handlers have the following advantages:

1. You can output error information to specified files, databases, emails, logs, etc. to facilitate error location and processing.
2. You can control error information more flexibly, such as filtering unnecessary information, counting the number of errors, selecting different processing methods, etc.
3. can improve the maintainability and readability of the code, because specific error handling functions can be implemented for different error types.

In short, through custom error handlers, we can handle error messages generated in PHP more efficiently and accurately, improving the robustness and maintainability of the code.

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