TopreventCSRFattacksinPHP,implementanti-CSRFtokens.1)Generateandstoresecuretokensusingrandom_bytes()orbin2hex(random_bytes(32)),savethemin$_SESSION,andincludetheminformsashiddeninputs.2)ValidatetokensonsubmissionbystrictlycomparingthePOSTtokenwiththe

There are many ways to merge two lists, and choosing the right way can improve efficiency. 1. Use number splicing to generate a new list, such as list1 list2; 2. Use = to modify the original list, such as list1 =list2; 3. Use extend() method to operate on the original list, such as list1.extend(list2); 4. Use number to unpack and merge (Python3.5), such as [list1,*list2], which supports flexible combination of multiple lists or adding elements. Different methods are suitable for different scenarios, and you need to choose based on whether to modify the original list and Python version.

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().

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.

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.

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.

loading="lazy" is an HTML attribute for and which enables the browser's native lazy loading function to improve page performance. 1. It delays loading non-first-screen resources, reduces initial loading time, saves bandwidth and server requests; 2. It is suitable for large amounts of pictures or embedded content in long pages; 3. It is not suitable for first-screen images, small icons, or lazy loading using JavaScript; 4. It is necessary to cooperate with optimization measures such as setting sizes and compressing files to avoid layout offsets and ensure compatibility. When using it, you should test the scrolling experience and weigh the user experience.