An odd character seems to appear in the return value of
create_function() (which should be of 'lambda_x' format
where x is an integer).  This character is causing eval() to
crap out when trying to evaluate the created function.  Just
before the 'l' is a character that looks like Pi in the
browser.  The only way I knew to find out what it was was to
urlencode() the return value and the strange character was
encoded to '%00'.  I'm no C coder, but the changes below
seemed to fix things.  

*** /tmp/zend_builtin_functions.c	Mon May  7 22:09:45 2001
--- /usr/local/src/php-4.0.5/Zend/zend_builtin_functions.c	Mon May  7 22:03:31 2001
***************
*** 965,974 ****
  		}
  		function_add_ref(func);
  
! 		function_name = (char *)
emalloc(sizeof("0lambda_")+MAX_LENGTH_OF_LONG);
  
  		do {
! 	
	sprintf(function_name, "%clambda_%d", 0, ++EG(lambda_count));
  	
	function_name_length = strlen(function_name+1)+1;
  		} while (zend_hash_add(EG(function_table), function_name,
function_name_length+1, func, sizeof(zend_function),
NULL)==FAILURE);
  		zend_hash_del(EG(function_table), LAMBDA_TEMP_FUNCNAME,
sizeof(LAMBDA_TEMP_FUNCNAME));
--- 965,974 ----
  		}
  		function_add_ref(func);
  
! 		function_name = (char *)
emalloc(sizeof("lambda_")+MAX_LENGTH_OF_LONG);
  
  		do {
! 	
	sprintf(function_name, "lambda_%d", ++EG(lambda_count));
  	
	function_name_length = strlen(function_name+1)+1;
  		} while (zend_hash_add(EG(function_table), function_name,
function_name_length+1, func, sizeof(zend_function),
NULL)==FAILURE);
  		zend_hash_del(EG(function_table), LAMBDA_TEMP_FUNCNAME,
sizeof(LAMBDA_TEMP_FUNCNAME));