If I feed to PHP:

$01 = 1;

it crashes with:

Program received signal SIGSEGV, Segmentation fault.
_mem_block_check (ptr=0x0, silent=1, __zend_filename=0x80d2a00 "zend_hash.c", 
    __zend_lineno=594, __zend_orig_filename=0x0, __zend_orig_lineno=0)
    at zend_alloc.c:483
483		switch (p->magic) {
(gdb) bt
#0  _mem_block_check (ptr=0x0, silent=1, 
    __zend_filename=0x80d2a00 "zend_hash.c", __zend_lineno=594, 
    __zend_orig_filename=0x0, __zend_orig_lineno=0) at zend_alloc.c:483
#1  0x807ae78 in _efree (ptr=0x0, __zend_filename=0x80d2a00 "zend_hash.c", 
    __zend_lineno=594, __zend_orig_filename=0x0, __zend_orig_lineno=0)
    at zend_alloc.c:170
#2  0x80880e6 in zend_hash_destroy (ht=0x8103b84) at zend_hash.c:594
#3  0x805a03d in php_rshutdown_basic (type=1, module_number=18)
    at basic_functions.c:422
#4  0x8085890 in module_registry_cleanup (module=0x811d660) at zend_API.c:847
#5  0x8088373 in zend_hash_apply (ht=0x8106020, 
    destruct=0x808586c <module_registry_cleanup>) at zend_hash.c:708
#6  0x808526e in zend_deactivate () at zend.c:459
#7  0x8075904 in php_request_shutdown (dummy=0x0) at main.c:750
#8  0x8059ea2 in main (argc=2, argv=0xbffff8b4) at cgi_main.c:507

If I feed some garbage to PHP (like php < /usr/bin/php) it crashes in the same place, for what it worth.