exit() is a function in PHP that is used to terminate script execution immediately. Common uses include: 1. Terminate the script in advance when an exception is detected, such as the file does not exist or verification fails; 2. Output intermediate results during debugging and stop execution; 3. Call exit() after redirecting in conjunction with header() to prevent subsequent code execution; In addition, exit() can accept string parameters as output content or integers as status code, and its alias is die().

Enums in Java are special classes that represent fixed number of constant values. 1. Use the enum keyword definition; 2. Each enum value is a public static final instance of the enum type; 3. It can include fields, constructors and methods to add behavior to each constant; 4. It can be used in switch statements, supports direct comparison, and provides built-in methods such as name(), ordinal(), values() and valueOf(); 5. Enumeration can improve the type safety, readability and flexibility of the code, and is suitable for limited collection scenarios such as status codes, colors or week.

To merge two PHP arrays and keep unique values, there are two main methods. 1. For index arrays or only deduplication, use array_merge and array_unique combinations: first merge array_merge($array1,$array2) and then use array_unique() to deduplicate them to finally get a new array containing all unique values; 2. For associative arrays and want to retain key-value pairs in the first array, use the operator: $result=$array1 $array2, which will ensure that the keys in the first array will not be overwritten by the second array. These two methods are applicable to different scenarios, depending on whether the key name is retained or only the focus is on

The rational use of semantic tags in HTML can improve page structure clarity, accessibility and SEO effects. 1. Used for independent content blocks, such as blog posts or comments, it must be self-contained; 2. Used for classification related content, usually including titles, and is suitable for different modules of the page; 3. Used for auxiliary information related to the main content but not core, such as sidebar recommendations or author profiles. In actual development, labels should be combined and other, avoid excessive nesting, keep the structure simple, and verify the rationality of the structure through developer tools.

The way to process raw POST data in PHP is to use $rawData=file_get_contents('php://input'), which is suitable for receiving JSON, XML, or other custom format data. 1.php://input is a read-only stream, which is only valid in POST requests; 2. Common problems include server configuration or middleware reading input streams, which makes it impossible to obtain data; 3. Application scenarios include receiving front-end fetch requests, third-party service callbacks, and building RESTfulAPIs; 4. The difference from $_POST is that $_POST automatically parses standard form data, while the original data is suitable for non-standard formats and allows manual parsing; 5. Ordinary HTM

There are two ways to create an array in PHP: use the array() function or use brackets []. 1. Using the array() function is a traditional way, with good compatibility. Define index arrays such as $fruits=array("apple","banana","orange"), and associative arrays such as $user=array("name"=>"John","age"=>25); 2. Using [] is a simpler way to support since PHP5.4, such as $color

When the Windows search bar cannot enter text, common solutions are: 1. Restart the Explorer or computer, open the Task Manager to restart the "Windows Explorer" process, or restart the device directly; 2. Switch or uninstall the input method, try to use the English input method or Microsoft's own input method to eliminate third-party input method conflicts; 3. Run the system file check tool, execute the sfc/scannow command in the command prompt to repair the system files; 4. Reset or rebuild the search index, and rebuild it through the "Index Options" in the "Control Panel". Usually, we start with simple steps first, and most problems can be solved step by step.

array_filter is used to filter elements in an array that meet the criteria. It is useful when you need to filter null values, specific values, or filter by rules, such as string length, such as removing false values, retaining even numbers, or long strings. When using it, you can choose whether to pass the callback function: if you do not pass, false values ??such as false, null will be automatically filtered; if you pass, it will decide whether to keep it based on the callback return true or false. In addition, the filtering can be done by combining the key name with the ARRAY_FILTER_USE_BOTH parameter and the index can be reset using array_values.