1. Basic usage of substr function The substr function in PHP is defined as follows:

1. Problem manifestation When you call the ftp_systype() function, the expected return is similar to the following:

socket_last_error() is a very important debugging tool when programming networks using PHP. It can help us get the error code that occurred in the latest socket operation and then locate the problem. However, many developers have reported that: socket_last_error() always returns 0 even though an exception appears, which makes debugging extremely difficult. This article will analyze the root causes of this phenomenon in depth and key points you may overlook.

What is rawurldecode? The rawurldecode() function is used to decode URL-encoded strings. It converts the percent sign encoding in the URL (such as %20 for space) back to the original character. Unlike urldecode(), rawurldecode() will handle encoding strictly in accordance with the RFC 3986 standard, especially when dealing with spaces, it decodes %20 into spaces without converting the plus sign (+) into spaces.

In PHP, unregister_tick_function is a function used to log out the previously registered tick function. The tick function is a mechanism of PHP that monitors or processes the code execution status by periodically triggering callback functions during code execution. It is usually used in conjunction with the declare(ticks=N) statement.

1. Understand timezone_identifiers_list timezone_identifiers_list is a built-in PHP function to obtain all available time zone identifiers. Its usage is very simple:

In PHP, the imagewbmp() function is used to output or save an image in WBMP format. WBMP (Wireless Bitmap) is a black and white bitmap format that is often used for image display on mobile devices. Understanding the parameters of the imagewbmp() function and its correct usage is very important for image processing and generation related projects.

Basic usage examples Suppose we have two arrays, one is the student name and the other is the corresponding grades, and we want to combine them into an associative array of "name => grades":

What is output buffering? By default, echo or other output commands will directly send the content to the client (browser). However, after turning on the output buffering, the output will not be sent immediately, but will be saved in the buffer first and will not be output until the buffer is cleared or the script is finished. In this way, we can capture, modify and even redirect the output content during the script running.

Question description Assume that you are trying to create a directory using the following code:

1. Basics of tick function registration and cancellation First, let’s review the basic usage of tick function registration and cancellation:

What is array_diff_assoc array_diff_assoc is a PHP built-in function that compares the keys and values ​​of two (or more) associative arrays, returning key-value pairs that are in the first array but not in other arrays. It not only compares values, but also compares key names.

In PHP programming, is_null and empty are two commonly used functions that are used to judge the state of variables, but their functions are obviously different from those used in the scenario. This article will compare these two functions in detail to help you understand their differences and use them reasonably in actual development.

mb_strcut is a very practical function when dealing with multibyte characters (such as Chinese, Japanese, Korean, etc.) in PHP. Unlike substr, it ensures that multi-byte characters will not be truncated, thus avoiding garbled problems. This article will explain in detail how to correctly use mb_strcut to intercept multi-byte strings and demonstrate them in combination with actual cases.

In PHP programming, you often encounter scenarios where you need to determine whether an object contains a certain attribute. Although it can be used to judge it using isset() or property_exists(), the behavior of the two is slightly different, especially when dealing with properties of the class. This article will focus on how the property_exists() function is used and what to note in actual applications.

1. What is stream_copy_to_stream? stream_copy_to_stream is a function provided by PHP, and the prototype is as follows:

1. Introduction to uksort() function uksort(array &$array, callable $callback): The bool function sorts the keys of an array. $callback is a user-defined comparison function that accepts two key names as parameters, returns values ​​less than, equal to or greater than zero, and determines the sorting order.

Among PHP's string processing functions, strpos and strpos are two often used functions. They look almost the same, only one letter apart, but in fact there is a key difference. This article will take you to thoroughly understand the similarities and differences between these two functions from the aspects of usage, differences, precautions, etc.

1. Introduction to dir() function The dir() function is used to open a directory handle and return a Directory object. You can read the file and subdirectory names in the directory one by one through the read() method of this object.

Function introduction getservbyname() getservbyname(string $service, string $protocol): int|false