PHP 中的 error_reporting()

在 PHP 的各種等級的錯誤中，error_reporting 是 PHP 中的一個函數，它指示報告的錯誤是什麼，並確定執行時的 error_reporting 指令。使用此函數，我們可以為腳本所需的持續時間（通常是執行時間）設定規定的等級。它根據給定的輸入返回舊的錯誤報告級別，或在未給出參數時返回當前的報告級別。

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帶參數的語法

以下是帶參數的語法：

文法：

error_reporting(level)

參數：

只有一個參數級別，該參數級別是可選的並且其輸入函數採用。它指定當前腳本的錯誤報告等級。接受的值為常數名稱和值編號。

注意： 為了確保 PHP 未來版本的相容性，建議使用命名常數。

有一些預定義常數，其說明如下：

1。 E_Error：這些表示無法復原的致命執行階段錯誤，​​且腳本執行將停止。

2。 E_Warning： 這些是非致命錯誤，腳本將繼續執行。

3。 E_Parse： 這顯示僅由解析器產生的編譯時解析錯誤。

4。 E_Notice：這會發出執行時間通知，表示腳本發現了一些顯示錯誤的內容，但在執行正常腳本時也可能會發生這種情況。

5。 E_Core_Error: 在 PHP 初始啟動期間，可能會出現一些由 PHP 核心產生的致命錯誤。

6。 E_Core_Warning：這顯示了 PHP 初始啟動期間出現的非致命錯誤，也是由 PHP 核心產生的。

7。 E_Compile_Error：這些顯示編譯期間發生的致命錯誤。這些是由 Zend 腳本引擎產生的。

8。 E_Compile_Warning：與上方類似，這些顯示編譯時警告或可稱為非致命錯誤，也由 Zend 腳本引擎產生。

9。 E_User_Error：顯示使用者產生的錯誤。這與 E_ERROR 類似，只不過它是使用 PHP 程式碼中的 PHP 函數產生的。

10。 E_All：這就像上述所有內容的組合，支援 E_STRICT 以外的所有錯誤和警告。

傳回值：

error_reporting 函數給予舊的報告等級或目前的錯誤報告等級（如果沒有給出參數）。

PHP 中 error_reporting 的工作原理

此功能可讓開發人員實際控制不同類型的錯誤以及應用程式中將拋出多少此類錯誤。此函數設定一個 error_reporting 指令，該指令將出現在 PHP ini 設定檔中。

error_reporting(0);

• When 0 is passed to the error reporting function it removes all warnings, errors, parse related messages and notices, if any. Instead of having to include this line in each of the PHP code files, it is practical to have it added and to turn off these report messages in the ini file present or in the .htaccess.

error_reporting(E_NOTICE);

• In PHP the variables can be used even when not declared. But this practice is not feasible as the undeclared variables may cause application related issues if it is used in conditional statements and loops. This may also take place because of the spelling mismatch between the declared variables and of that being used for conditions and loops. When this E_NOTICE will be passed into the error_reporting function, only then these undeclared variables will be shown in the web application.

error_reporting(E_ALL & ~E_NOTICE);

• This error reporting function helps to filter out the errors which can be displayed. The “~” character here means the “not/no” and hence ~E_NOTICE here means to not show any notices. Here the “&” character represents “true for all” whereas “|” means as long as one of the parameters is true. They are exactly similar to the functions AND and OR in PHP.

error_reporting(E_ALL);
error_reporting(-1);
ini_set('error_reporting', E_ALL);

• All of the above lines serve the same purpose i.e. show all the errors. E_ALL is the most widely used function among all others by developers to display error messages as it is more comprehensible and intelligible.

Error Logging in PHP using error_log() Function

It happens so that during the production phase, error messages are to be hidden from the end-users but this information is needed to be registered for tracing purpose. And the best way to record these errors on the production web application is to write and store in log files.

An easy way to log these is by using the error_log function which takes our parameters as input. The only mandatory parameter here is the first one which contains details about the errors and what all to be logged. Other parameters like the type, destination, and header are non-mandatory here for this function.

error_log("Error found!", 0);

• The type parameter will be set to 0 by default if not given, and the log information will be appended at the end of the log file generated in the webserver.

error_log("Error information being emailed!", 1, "[email protected]");

• The type parameter here is 1 will email this log specified in the 3rd parameter which is the email id. For this to work, the PHP ini file must be having a correct SMTP configuration to send out emails. Some of the parameters required for these include host, encryption type, port, password and username.

error_log("Write errors to this file", 3, "https://cdn.educba.com/tmp/errorfile.log")<em>;</em>

• The same error logs can also be written down to the required file whose path will be given in the third parameter. Make sure the given path has all required permissions.

Example of error_reporting() in PHP

Given below is the example:

Code:

<?php
$a = 1;
trigger_error("user warning!", E_USER_WARNING);
$a = 2;
echo "Value of $a is ${$a}";
error_reporting(0);
error_reporting(E_ALL);
?>

Output:

Advantages of using error_reporting function in PHP

• error_reporting is good for debugging purposes and for developing web application.
• Each and every error can be logged and fixed as soon as it happens using this function.
• To not show it to the end-user, make sure you redirect the errors to a log file while releasing it.

Conclusion

Hence we can say that error_reporting() function in PHP are therefore helpful in cases when there are a lot of problems with the PHP web application and we need to display all of these errors and warnings either for development or debugging purposes. It is a function we can enable different kinds of warnings or error messages and most of them are as discussed above.

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