The function and precautions of adding @ symbol before PHP class method

In PHP, we can add the @ symbol to class methods to suppress warning or error messages that may be generated. The function of the @ symbol seems simple, but there are many issues that need attention in actual development.

Before introducing how to use the @ symbol correctly, let’s first understand its function. In PHP, if we call a method, some warning or error messages may be generated in the method, such as trying to access an undefined variable, opening a non-existent file, etc. If we do not handle these warning or error messages, the program will terminate execution due to these problems. In some cases, we may not want these warnings or error messages to affect the execution results of the program. In this case, we can add the @ symbol to discard the generated warning or error messages without affecting the continued execution of the program.

Let's look at an example:

class MyClass {
    public function foo() {
        @include 'nonexistfile.php';
        echo 'hello world';
    }
}

$obj = new MyClass();
$obj->foo();

In the above code, we called the include function in the foo method of the MyClass class, including a file that does not exist. If we do not add the @ symbol, we will see a warning message "Warning: include(nonexistfile.php) failed to open stream...". But if we add the @ symbol, we will not see this warning message, and the program will directly output "hello world".

Although the @ symbol seems to be a convenient way, in actual development, we need to use it carefully to avoid some problems that are difficult to debug. Let’s look at a few issues that need attention.

1. Easy to ignore error messages

After we add the @ symbol, the program will no longer print out the warning or error message generated, which may cause us to ignore it some problems. For example, in the above example, we included a non-existent file in the foo method of MyClass, but due to the addition of the @ symbol, the program directly outputs "hello world". We cannot know what impact the failure of including the file will have on the program. , and it is impossible to know whether the program has other problems at this location.

2. Affects the readability of the code

When we read the code, if we use a lot of @ symbols, it will affect the readability of the code and be easily hidden. Some details. For example, the following example:

public function doSomething() {
    $result = @mysql_query($sql);
    if ($result === false) {
        // handle error
    }
}

In this example, we use the @ symbol to suppress warning or error messages that may be generated by the mysql_query function. However, in the subsequent code, we need to determine whether the mysql_query function is successfully executed. Due to the hidden effect of the @ symbol, we need to identify the error message by explicitly determining whether $result is equal to false. This will make the code verbose and also There may be some hard-to-identify problems hidden behind the code.

3. Differences in different environments

In different PHP environments, the use of the @ symbol may be handled differently. In some PHP versions, if the @ symbol is used, error information will be output directly to standard error, which will affect some codes that need to detect standard error. In addition, the @ symbol can only suppress ordinary error messages. If we use functions such as Set_error_handler, the @ symbol will no longer have any effect.

Therefore, in actual development, we need to avoid using the @ symbol as much as possible, and when we need to use it, we need to carefully handle possible problems. For example, we can use error levels such as E_ERROR and E_PARSE to control the types of errors that need to be suppressed, or we can use the try...catch statement to capture thrown exception information. These methods can avoid the problem while ensuring the normal operation of the program. Hide potential problems behind code.

In short, although the @ symbol looks very simple, there are many problems that need to be paid attention to in actual development. We need to clearly choose where the @ symbol should be used after weighing the pros and cons, and when using it, we also need to clearly control the problems that may arise to ensure the readability and stability of the code.

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