What is a php UDF? Php UDF concepts

Generally, PHP built-in functions are used. However, the true functions of programming languages are implemented by creating their own functions. most of the functions provided by PHP are basic functions, such as operating arrays, accessing databases, and reading and writing files. Before introducing php user-defined functions, let's introduce them first.

FunctionSome statements with certain functions are organized together. The purpose of defining a function is to divide the program by function to facilitate the use, management, reading, and debugging of the program.

There are two types of functions:

One is a function written by someone else or provided inside the system. you only need to know what the function is for, and you will know how to use it. you don't need to go into the implementation of the function, for example, various string functions and array functions used have the following features:

1. specific functions can be executed.

2. all have special names

3. there are more or less parameters.

4. most functions return values and perform specific operations even if they do not.

5. You do not need to know the internal implementation logic of the function.

Another function is defined by yourself to meet your unique needs. The concept may be abstract and hard to understand. we can think of a function as a juicer. the parameter is like the fruit we put in, and the code executed in the function is like the stirring of a mixer. Different parameters make the function return different results, just as Apple juice does not appear after oranges are placed. The function can also accept multiple parameters, just like a mixed juice.

The function is only called by function name, but we do not need to know how the code in the function is defined. Similarly, we do not need to understand the working principle of the juicer. Functions exist in most programming languages and are used to separate code that can complete independent and explicit tasks. The function name must start with a letter or underline followed by letters, numbers, or Underscores. In addition, the function name is case insensitive.

Therefore, a function is defined as a named, independent code segment. it executes a specific task and may return a value to the program that calls it. PHP's modular program structure is implemented through functions or objects. functions divide complicated PHP programs into several functional modules, and each module is compiled into a PHP function, then, some large PHP scripts can be written by calling the function in the script and calling the function in the function.

Generally, PHP built-in functions are used. However, the true functions of programming languages are implemented by creating their own functions. most of the functions provided by PHP are basic functions, such as operating arrays, accessing databases, and reading and writing files. However, in real projects, PHP functions cannot meet our needs. we cannot find functions that can be used to process contracts, functions that do not calculate attendance, and functions that do not print data tables.

During the development process, you often need to repeat some operations, such as data query and character operations. if you re-enter the code for each module operation, it will not only cause a headache for programmers, it also has a great impact on the code maintenance and running effect. Fortunately, we are not limited to PHP built-in functions. we can write our own functions to complete any task. this is a user-defined function.

When writing a function, you must first specify what you want this function to do, what you want to achieve, and what functions you want to implement. after knowing this, the idea will be clear when writing the function, it won't be too difficult to write the code. In php, in addition to thousands of system functions that can be directly used by friends, you can also create custom functions based on your module requirements.

The so-called system functions are directly usable functions provided in php. Each of these system functions is a complete code segment that can complete a specified task. Learn more about one of the system functions and learn more about one php function. In the development process, some common functions can be completed by calling system functions. If some functional modules do not provide system functions in php, you need to define functions by yourself. Generally, the execution efficiency of system functions is higher than that of user-defined functions, but there is no obvious difference between the two functions in the program.

Php user-defined functions have the following advantages:

A. re-use the program

B. improve code maintainability

C. improve development efficiency

D. enhanced reliability

E. Complexity of control program design

The following is a simple php UDF output example.

Output result: this is a UDF.

The preceding section describes how to declare php UDFs in the next chapter.

What is the php UDF above? For more details about php UDF concepts, see other related articles in the first PHP community!