php study notes--error
Different error handling methods: Simple die() statement to customize error function and error trigger error reporting Basic error handling: use the die() functionif(!file_exists("welcome.txt")){ die("FIle not found"); }else{ $file=fopen("welcome.txt","r"); }
or $file=fopen("webdictionary.txt","r") or die("Unable to open file!");
die(status): If status is a string, this function will output the string before ejecting. If status is a certificate, this value will be used as the exit status. The exit status has a value between 0 and 254. Exit status 255 is reserved by PHP and will not be used. Status 0 is used to terminate the program successfully.
Create a custom error handler: The function must be able to handle at least two parameters (error level and error message), but can accept up to five parameters (optional: file, line-number and error context). error_function(error_level,error_message,error_file,error_line,error_context)//Error reporting level, error message, file name and line number to send the error, specify an array (containing each variable used when the error occurs and their values) )
value | Constant | Description | ||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2 | E_WARNING | Nonfatal run-time error. Do not pause script execution. | ||||||||||||||||||||||||
8 | E_NOTICE |
|
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256 | E_USER_ERROR | Fatal user-generated error. This is similar to E_ERROR set by the programmer using the PHP function trigger_error(). |
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512 | E_USER_WARNING | Non-fatal user-generated warning. This is similar to the E_WARNING set by the programmer using the PHP function trigger_error(). |
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1024 | E_USER_NOTICE | User-generated notifications. This is similar to E_NOTICE set by the programmer using the PHP function trigger_error(). |
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4096 | E_RECOVERABLE_ERROR | Catchable fatal error. Like E_ERROR, but can be caught by a user-defined handler. (see set_error_handler()) |
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8191 | E_ALL | All errors and warnings except level E_STRICT. (In PHP 6.0, E_STRICT is part of E_ALL) |
function customError($errno,$errstr){ echo "Error:[$errno] $errstr
"; echo "Ending Script"; die(); }
When the above error is triggered, it gets the error level and error message. It then prints the error level and message, and terminates the script. Now that we have created an error handling function, we need to determine when to fire it.
Set Error Handler: PHP's default error handler is the mole's error handler. Error handlers can be modified to apply only to certain errors, so that the script can handle different errors in different ways.
In this case, we are going to use our custom error handler for all errors. set_error_handle(“customError”); When handling all errors, set_error_handler() requires only one parameter, and a second parameter can be added to specify the error level.
Trigger error:
Triggers an error when the user's input is invalid. Completed by trigger_error(). $test=2; if($test>1){ trigger_error("Value must be 1 or below");//An error is triggered when it is greater than 1 }
Possible error types:
E_USER_ERROR: E_USER_WARNING: E_USER_NOTICE:
TechArticle

Reasons for PHPSession failure include configuration errors, cookie issues, and session expiration. 1. Configuration error: Check and set the correct session.save_path. 2.Cookie problem: Make sure the cookie is set correctly. 3.Session expires: Adjust session.gc_maxlifetime value to extend session time.

Methods to debug session problems in PHP include: 1. Check whether the session is started correctly; 2. Verify the delivery of the session ID; 3. Check the storage and reading of session data; 4. Check the server configuration. By outputting session ID and data, viewing session file content, etc., you can effectively diagnose and solve session-related problems.

Multiple calls to session_start() will result in warning messages and possible data overwrites. 1) PHP will issue a warning, prompting that the session has been started. 2) It may cause unexpected overwriting of session data. 3) Use session_status() to check the session status to avoid repeated calls.

Configuring the session lifecycle in PHP can be achieved by setting session.gc_maxlifetime and session.cookie_lifetime. 1) session.gc_maxlifetime controls the survival time of server-side session data, 2) session.cookie_lifetime controls the life cycle of client cookies. When set to 0, the cookie expires when the browser is closed.

The main advantages of using database storage sessions include persistence, scalability, and security. 1. Persistence: Even if the server restarts, the session data can remain unchanged. 2. Scalability: Applicable to distributed systems, ensuring that session data is synchronized between multiple servers. 3. Security: The database provides encrypted storage to protect sensitive information.

Implementing custom session processing in PHP can be done by implementing the SessionHandlerInterface interface. The specific steps include: 1) Creating a class that implements SessionHandlerInterface, such as CustomSessionHandler; 2) Rewriting methods in the interface (such as open, close, read, write, destroy, gc) to define the life cycle and storage method of session data; 3) Register a custom session processor in a PHP script and start the session. This allows data to be stored in media such as MySQL and Redis to improve performance, security and scalability.

SessionID is a mechanism used in web applications to track user session status. 1. It is a randomly generated string used to maintain user's identity information during multiple interactions between the user and the server. 2. The server generates and sends it to the client through cookies or URL parameters to help identify and associate these requests in multiple requests of the user. 3. Generation usually uses random algorithms to ensure uniqueness and unpredictability. 4. In actual development, in-memory databases such as Redis can be used to store session data to improve performance and security.

Managing sessions in stateless environments such as APIs can be achieved by using JWT or cookies. 1. JWT is suitable for statelessness and scalability, but it is large in size when it comes to big data. 2.Cookies are more traditional and easy to implement, but they need to be configured with caution to ensure security.


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