Step by Step solution about How to resolve the algorithm Call a foreign-language function step by step in the PHP programming language

This PHP code uses the Foreign Function Interface (FFI) extension to call the C function _strdup from the Microsoft C Runtime library (msvcrt.dll) to duplicate a string. Here's a detailed explanation of what it does:

1. $ffi = FFI::cdef("char *_strdup(const char *strSource);", "msvcrt.dll");:

   • This line initializes the FFI extension and defines a custom type, char*, which represents a C-style string pointer.
   • It declares the _strdup function from the msvcrt.dll library, which takes a const char* (a pointer to a constant C-style string) as input and returns a pointer to a new, duplicated string.

2. $cstr = $ffi->_strdup("success");:

   • This line calls the _strdup function with the string "success" as the input.
   • The $ffi->_strdup syntax uses the FFI's function calling syntax to invoke _strdup with the string "success" as the argument.
   • $cstr now holds a pointer to a newly allocated copy of the "success" string.

3. $str = FFI::string($cstr);:

   • This line converts the pointer stored in $cstr (which points to a C-style string) to a PHP string using the FFI::string function.
   • $str now holds the string "success" as a PHP string.

4. echo $str;:

   • This line prints the $str variable to the standard output, which would display "success".

5. FFI::free($cstr);:

   • This line frees the memory allocated for the duplicated string pointed to by $cstr.
   • It's important to explicitly free this memory to prevent memory leaks.

In summary, this code demonstrates how to use the FFI extension to call a C function, duplicate a string using _strdup, and then access and use the duplicated string in PHP. It illustrates how FFI enables interoperability between PHP and C code.

$ffi = FFI::cdef("char *_strdup(const char *strSource);", "msvcrt.dll");

$cstr = $ffi->_strdup("success");
$str = FFI::string($cstr);
echo $str;
FFI::free($cstr);