Does php have no main function?

There is no main function in PHP; this function is often used in Java and C languages, and is also called the main function. As the only entry point for most C programs, it requires a return value. Returning 0 represents the program. If normal execution is successful, returning a non-zero value indicates that the program ends abnormally; however, this function does not exist in PHP.

The operating environment of this article: Windows 10 system, PHP version 8.1, Dell G3 computer

Does php not have a main function?

php does not have a main function

Introduction to the main function

The main function, also known as the main function, is the only entry point for most C programs. If a return value is required, the return value is returned to (such as the operating system) to indicate the execution status of the program. Returning 0 means that the program is successfully executed normally, and returning a non-0 value means that the program ends abnormally. Therefore, the return value needs to be an integer, so there is the specification of int main().

If you use void main(), it means that the main function has no return value. Although the program can be compiled and run successfully, it is not conducive for the activator of the program to judge its status. This is not suitable for large projects consisting of many C programs. It can be fatal.

Especially starting from the C99 standard (the second edition of the official C language standard formulated in 1999), int main() must be used. If the return 0; language is not added, C99 requires the compiler to automatically add it (write it yourself. good habits). If only main() is declared, the system defaults to int main(). void main() should never be used, because the main function must have a return value to indicate the running status of the program (it is a good habit not to use void main() in your code).

Definition

In the latest C99 standard, only the following two definitions are correct:

int main(void)
int main(int argc, char *argv[]) // char *argv[]可以写成char **argv

1. Parameters

void: does not accept any parameters;

argc: represents the number of parameters passed to the program by the environment in which the program is running;

argv: a pointer to the first element of the array of argc 1 pointers. The last element of the array is a null pointer, and if there are previous elements, they point to strings representing the parameters passed to the program from the host environment. If argv[0] is not a null pointer (or argc>0), it points to a string representing the program name. This string is empty if the program name is not available from the host environment.

2. Return value

The return value will be used as a parameter for the implicit call to exit(). Values ​​of 0 and EXIT_SUCCESS indicate successful termination, and values ​​other than 0 and EXIT_FAILURE indicate unsuccessful termination.

EXIT_SUCCESS, EXIT_FAILURE, defined in the header file 8e359799bdf1a571032ba13cc96acda9:

#define EXIT_SUCCESS 0
#define EXIT_FAILURE 1

The EXIT_SUCCESS and EXIT_FAILURE macros expand integer expressions that can be used as exit parameters (and thus as returned from the main function value) and indicates the program execution status. EXIT_SUCCESS indicates that the program execution is successful, and EXIT_FAILURE indicates that the program execution is unsuccessful.

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