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This article will explain in detail how to call the FFI extension in PHP. The content of the article is of high quality, so the editor shares it for you as a reference. I hope you will have some understanding of the relevant knowledge after reading this article.

What is FFI?

FFI, Foreign Function Interface, external function interface. This extension allows us to load some common libraries (.dll, .so), which means that we can call some C data structures and functions. It is already an extension released with the PHP source code, and it can be compiled directly into PHP programs by adding-with-ffi at compile time.

We already have a compiled PHP here, so we can find the extension directly and install it with a simple extension installation step.

Cd php-7.4.4/ext/ffi/

Phpize

. / configure

Make & & make install

Remember to open the extension in the php.ini file after the installation is complete. One thing to note about this extension is that it has a configuration item called ffi.enable, which by default has a value of "preload", which enables FFI only in the CLI SAPI environment. Of course, we can also change it to "true" or "false" to turn it on and off. Setting it to "true" will enable this extension in any environment.

Call the function of C using FFI

Next, take a brief look at how it calls C's functions.

/ / create a FFI object, load libc and import the printf function

$ffi_printf = FFI::cdef (

"int printf (const char * format,...);", / / definition rules of C

"libc.so.6"); / / specify the libc library

/ / call the printf function of C

$ffi_printf- > printf ("Hello% s!\ n", "world"); / / Hello World

/ / load math and import pow function

$ffi_pow = FFI::cdef (

"double pow (double x, double y);"

"libboost_math_c99.so.1.66.0")

/ / the pow function of C is called here, not PHP's own

Echo $ffi_pow- > pow (2mam 3), PHP_EOL; / / 8

We created two objects and called the printf () and pow () functions of C, respectively. FFI::cdef () is used to create a FFI object that takes two parameters, one of which is a string containing a sequence of declarations in the regular C language (types, structures, functions, variables, and so on). In fact, this string can be copied and pasted from the C header file. The other parameter is the name of the shared library file to load and define the link. That is, the .dll or .so file we need, which corresponds to our declaration string. For example, there is no calculation function such as pow () in libc.so.6, so we need to find the C language calculation function library related to math.

Define variables and arrays

Of course, FFI can also define variables and arrays.

/ / create an int variable

$x = FFI::new ("int")

Var_dump ($x-> cdata); / / int (0)

/ / assign values to variables

$x-> cdata = 5

Var_dump ($x-> cdata); / / int (5)

/ / calculate variables

$x-> cdata + = 2

Var_dump ($x-> cdata); / / int (7)

/ / combine the above two FFI object operations

Echo "pow value:", $ffi_pow- > pow ($x-> cdata, 3), PHP_EOL

/ / pow value:343

$ffi_printf- > printf ("Int Pow value is:% f\ n", $ffi_pow- > pow ($x-> cdata, 3))

/ / Int Pow value is: 343.000000

/ / create an array

A = FFI::new ("long [1024]")

/ / assign values to the array

For ($I = 0; $I < count ($a); $iTunes +) {

$a [$I] = $I

}

Var_dump ($a [25]); / / int (25)

$sum = 0

Foreach ($an as $n) {

$sum + = $n

}

Var_dump ($sum); / / int (523776)

Var_dump (count ($a)); / / int (1024) array length

Var_dump (FFI::sizeof ($a)); / / int (8192), memory size

Use the FFI::new () function to create a C data structure, the variable declaration, whose contents will be stored in the cdata property. The array can directly manipulate the return value of this function. Of course, when we want to end the use, we still need to use FFI::free () to release variables, just like the development of C language.

On how to call the FFI extension in PHP to share here, I hope the above content can be of some help to you, can learn more knowledge. If you think the article is good, you can share it for more people to see.

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