SDL extension for PHP

I am running PHPSDL from SVN on PHP 4.4.7 under Slackware Linux 12.0
(kernel 2.6.21.5) with SDL 1.2.11, and any trying to free an allocated
surface (created from a BMP) causes a segmentation fault.

Sample Code:
<?php
if(!extension_loaded("sdl")) dl("sdl.so");
register_shutdown_function("SDL_Quit");
echo "SDL_Init...";
if (SDL_Init(SDL_INIT_VIDEO) < 0) die("Unable to initialize SDL");
echo "Done\n";

echo "SDL_SetVideoMode...";
$video = SDL_SetVideoMode(512, 384, 0, SDL_HWSURFACE);
if(!$video) die("Unable to initialize SDL Video");
echo "Done\n";

echo "SDL_LoadBMP...";
$bmp = SDL_LoadBMP("image.bmp");
echo "Done\n";

echo "SDL_FreeSurface...";
SDL_FreeSurface($bmp);
echo "Done\n";

?>

Output:
SDL_Init...Done
SDL_SetVideoMode...Done
SDL_LoadBMP...Done
SDL_FreeSurface...Segmentation fault

Output when run via GDB:

Starting program: /root/phpsdl/bin/php-sdl freesurface.php
[Thread debugging using libthread_db enabled]
[New Thread -1212336448 (LWP 22469)]
SDL_Init...Done
SDL_SetVideoMode...Done
SDL_LoadBMP...Done
SDL_FreeSurface...
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1212336448 (LWP 22469)]
0x0814ac21 in zend_hash_find (ht=0x81d6820, arKey=0xb7fd22ab "format",
nKeyLength=7, pData=0xbfccd000)
at /usr/local/src/php-4.4.7/Zend/zend_hash.c:900
900 p = ht->arBuckets[nIndex];
(gdb) where
#0 0x0814ac21 in zend_hash_find (ht=0x81d6820, arKey=0xb7fd22ab "format",
nKeyLength=7, pData=0xbfccd000)
at /usr/local/src/php-4.4.7/Zend/zend_hash.c:900
#1 0xb7fcb753 in zif_sdl_freesurface (ht=1, return_value=0x824b23c,
this_ptr=0x0, return_value_used=0, tsrm_ls=0x81d70a8)
at /usr/local/src/svn/phpsdl/source/sdl.c:2029
#2 0x081600f7 in execute (op_array=0x82392a4, tsrm_ls=0x81d70a8) at
/usr/local/src/php-4.4.7/Zend/zend_execute.c:1681
#3 0x08145cb6 in zend_execute_scripts (type=8, tsrm_ls=0x81d70a8,
retval=0x0, file_count=3)
at /usr/local/src/php-4.4.7/Zend/zend.c:939
#4 0x08116aba in php_execute_script (primary_file=0xbfccf820,
tsrm_ls=0x81d70a8)
at /usr/local/src/php-4.4.7/main/main.c:1757
#5 0x0816354a in main (argc=2, argv=0xbfccf8e4) at
/usr/local/src/php-4.4.7/sapi/cli/php_cli.c:838