PHP command line errors: things you may not know

This article will introduce some things you may not know about PHP command line errors.

As a popular server-side language, PHP generally runs on a Web server, but it can also be run directly on the command line. For example, under Linux or MacOS systems, we can enter "php in the terminal ” command to run PHP scripts directly.

However, just like in a web server, when we run PHP scripts from the command line, we will also encounter some errors. Here is some information you may not know about PHP command line errors:

1. Error messages are not automatically displayed

When we execute a PHP script from the command line When there is an error in the script, the error message is not automatically displayed on the screen as it is in the web server. This is because in the PHP environment on the command line, by default, PHP will output error information to the standard output stream (STDOUT) instead of the error output stream (STDERR).

Therefore, if you want to see PHP error information on the command line, you need to output the error information to the standard error stream. This can be achieved by adding the following code to the PHP script:

ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

These codes tell PHP to output error information to the error output stream and display all error information, including warnings and notifications. These codes should be placed at the beginning of the PHP script.

2. The program will still continue to execute

If you do not handle errors in the PHP command line script, the program will still continue to execute when an error occurs. This is because error handling in PHP command line scripts is different from that in web servers. If you want to handle errors on the command line, you can use a try-catch statement or a custom error handling function.

For example:

set_error_handler(function ($errno, $errstr, $errfile, $errline ) {
    echo "Error: [$errno] $errstr - $errfile:$errline";
    die();
});

These codes use a custom error handling function to handle error information and terminate program execution after the error handling is completed. This function should be added at the beginning of the PHP script.

3. PHP command line error information can be exported to a file

If you want to save the error information in the PHP command line to a file, you can use the redirection operation characters ">" and ">>". For example:

php script.php > output.log 2>&1

This command will redirect everything in the standard output stream and error output stream to a file named output.log. If you don't want to overwrite the original file content, you can use the ">>" operator.

4. Error messages can actually help you debug your program

The error message in the PHP command line may look confusing, but it can actually help you debug your program.

First of all, the error message will tell you where the problem occurred in the program, the type of error, file and line number, and the reason for the error. This information allows you to quickly identify the problem.

Secondly, the error message can also tell you the execution flow of the program. It can display the order of function calls and the parameter transfer between functions through the error stack, which is very helpful for understanding the execution flow of the program.

Conclusion:

When executing PHP scripts on the command line, you need to pay attention to how to handle PHP error messages. You can easily handle PHP errors from the command line by outputting error information to the standard error stream, customizing error handling functions, or using try-catch statements. In addition, you can use the redirection operator to export error information to a file for easy viewing and debugging.

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