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

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().

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.

To access session data in PHP, you must first start the session and then operate through the $_SESSION hyperglobal array. 1. The session must be started using session_start(), and the function must be called before any output; 2. When accessing session data, check whether the key exists. You can use isset($_SESSION['key']) or array_key_exists('key',$_SESSION); 3. Set or update session variables only need to assign values ??to the $_SESSION array without manually saving; 4. Clear specific data with unset($_SESSION['key']), clear all data and set $_SESSION to an empty array.

Recursive functions refer to self-call functions in PHP. The core elements are 1. Defining the termination conditions (base examples), 2. Decomposing the problem and calling itself recursively (recursive examples). It is suitable for dealing with hierarchical structures, disassembling duplicate subproblems, or improving code readability, such as calculating factorials, traversing directories, etc. However, it is necessary to pay attention to the risks of memory consumption and stack overflow. When writing, the exit conditions should be clarified, the basic examples should be gradually approached, the redundant parameters should be avoided, and small inputs should be tested. For example, when scanning a directory, the function encounters a subdirectory and calls itself recursively until all levels are traversed.

Installing Composer takes only a few steps and is suitable for Windows, macOS, and Linux. Windows users should download Composer-Setup.exe and run it to ensure that PHP is installed or XAMPP is used; macOS users need to execute download, verification, and global installation commands through the terminal; Linux users operate similarly to macOS, and then use the corresponding package manager to install PHP and download and move the Composer file to the global directory.

When you encounter the prompt "This operation requires escalation of permissions", it means that you need administrator permissions to continue. Solutions include: 1. Right-click the "Run as Administrator" program or set the shortcut to always run as an administrator; 2. Check whether the current account is an administrator account, if not, switch or request administrator assistance; 3. Use administrator permissions to open a command prompt or PowerShell to execute relevant commands; 4. Bypass the restrictions by obtaining file ownership or modifying the registry when necessary, but such operations need to be cautious and fully understand the risks. Confirm permission identity and try the above methods usually solve the problem.

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