PHP: Basic FFI usage

Basic FFI usage

Before diving into the details of the FFI API, lets take a look at a few examples demonstrating the simplicity of the FFI API usage for regular tasks.

Note:
Some of these examples require libc.so.6 and as such will not work on systems where it is not available.

Example #1 Calling a function from shared library

<?php
// create FFI object, loading libc and exporting function printf()
$ffi = FFI::cdef(
    "int printf(const char *format, ...);", // this is a regular C declaration
    "libc.so.6");
// call C's printf()
$ffi->printf("Hello %s!\n", "world");
?>

The above example will output:

Hello world!

Note:
Note that some C functions need specific calling conventions, e.g. __fastcall, __stdcall or ,__vectorcall.

Example #2 Calling a function, returning a structure through an argument

<?php
// create gettimeofday() binding
$ffi = FFI::cdef("
    typedef unsigned int time_t;
    typedef unsigned int suseconds_t;
 
    struct timeval {
        time_t      tv_sec;
        suseconds_t tv_usec;
    };
 
    struct timezone {
        int tz_minuteswest;
        int tz_dsttime;
    };
 
    int gettimeofday(struct timeval *tv, struct timezone *tz);    
", "libc.so.6");
// create C data structures
$tv = $ffi->new("struct timeval");
$tz = $ffi->new("struct timezone");
// call C's gettimeofday()
var_dump($ffi->gettimeofday(FFI::addr($tv), FFI::addr($tz)));
// access field of C data structure
var_dump($tv->tv_sec);
// print the whole C data structure
var_dump($tz);
?>

The above example will output something similar to:

int(0)
int(1555946835)
object(FFI\CData:struct timezone)#3 (2) {
  ["tz_minuteswest"]=>
  int(0)
  ["tz_dsttime"]=>
  int(0)
}

Example #3 Accessing existing C variables

<?php
// create FFI object, loading libc and exporting errno variable
$ffi = FFI::cdef(
    "int errno;", // this is a regular C declaration
    "libc.so.6");
// print C's errno
var_dump($ffi->errno);
?>

The above example will output:

int(0)

Example #4 Creating and Modifying C variables

<?php
// create a new C int variable
$x = FFI::new("int");
var_dump($x->cdata);

// simple assignment
$x->cdata = 5;
var_dump($x->cdata);

// compound assignment
$x->cdata += 2;
var_dump($x->cdata);
?>

The above example will output:

int(0)
int(5)
int(7)

Example #5 Working with C arrays

<?php
// create C data structure
$a = FFI::new("long[1024]");
// work with it like with a regular PHP array
for ($i = 0; $i < count($a); $i++) {
    $a[$i] = $i;
}
var_dump($a[25]);
$sum = 0;
foreach ($a as $n) {
    $sum += $n;
}
var_dump($sum);
var_dump(count($a));
var_dump(FFI::sizeof($a));
?>

The above example will output:

int(25)
int(523776)
int(1024)
int(8192)

Example #6 Working with C enums

<?php
$a = FFI::cdef('typedef enum _zend_ffi_symbol_kind {
    ZEND_FFI_SYM_TYPE,
    ZEND_FFI_SYM_CONST = 2,
    ZEND_FFI_SYM_VAR,
    ZEND_FFI_SYM_FUNC
} zend_ffi_symbol_kind;
');
var_dump($a->ZEND_FFI_SYM_TYPE);
var_dump($a->ZEND_FFI_SYM_CONST);
var_dump($a->ZEND_FFI_SYM_VAR);
?>

The above example will output:

int(0)
int(2)
int(3)

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User Contributed Notes 1 note

down

wowabbs+php at gmail dot com ¶

3 years ago

<?
  if(!dl("ffi")) // Load the extension
      throw new Exception('Cound not load the FFI extension.');

  function setWindowsDesktop($bmpFilePath)
  {
    define('SPI_SETDESKWALLPAPER'  , 0x14);
    define('SPIF_UPDATEINIFILE'    ,  0x1);
    define('SPIF_SENDWININICHANGE' ,  0x2);
    assert(File_Exists($bmpFilePath));
    
    // declare the Win32 API function used to change desktop settings.
    $User32 = FFI::cdef(<<<'IDL'
      int SystemParametersInfoA(int uAction, int uParam, char *lpvParam, int fuWinIni);
    IDL, 'User32.dll');
    $Kernel32 = FFI::cdef(<<<'IDL'
      int GetLastError();
    IDL, 'Kernel32.dll');
    // call the Windows API to update the desktop background.
    $Ret = $User32->SystemParametersInfoA(SPI_SETDESKWALLPAPER, 0, $bmpFilePath, SPIF_UPDATEINIFILE || SPIF_SENDWININICHANGE);
    if ($Ret == 0)
    {
      $Error = $Kernel32->GetLastError();
      throw new Exception("The call to the Windows API failed (error {$Error}).");
    }
  }
  
  $Url='https://www.php.net//images/news/phpkonf_2015.png';
  $Img=File_Get_Contents($Url);
  File_Put_Contents($File=basename($Url), $Img);
  setWindowsDesktop(realpath($File));
?>

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