This is because APD uses the function name __overridden__ for overridden function (php_apd.c:607). I am not sure as to why they have done this, but it would be fairly simple to patch it to generate a random name for the function.

On lines 610 and 611, there are two unused defined variable "temp_function_name" and "temp_function_name_length", it seems that these are intended for this exact use, but was never implemented.

Here is a patch for this, however, my experience with C is very limited, and with the zend engine, even less. Someone with more experiance may want to review this patch first:

--- orig.c	2008-06-17 10:27:26.000000000 +1000
+++ php_apd.c	2008-06-17 10:57:01.000000000 +1000
@@ -608,7 +608,7 @@
 PHP_FUNCTION(override_function)
 {
 	char *eval_code,*eval_name, *temp_function_name;
-	int eval_code_length, retval, temp_function_name_length;
+	int eval_code_length, retval, temp_function_name_length, i;
 	zval **z_function_name, **z_function_args, **z_function_code;
 	
 	if (ZEND_NUM_ARGS() != 3 || 
@@ -622,13 +622,22 @@
 	convert_to_string_ex(z_function_args);
 	convert_to_string_ex(z_function_code);
 
-	eval_code_length = sizeof("function " TEMP_OVRD_FUNC_NAME) 
+	temp_function_name_length = sizeof(TEMP_OVRD_FUNC_NAME);
+	temp_function_name = (char *) emalloc(temp_function_name_length + 10);
+	sprintf(temp_function_name, "%s", TEMP_OVRD_FUNC_NAME);
+	for(i = 0; i < 10; i++)
+		temp_function_name[temp_function_name_length+i-1] = 97 + (rand() % 26);
+	temp_function_name_length += 10;
+	temp_function_name[temp_function_name_length-1] = 0;
+
+	eval_code_length = sizeof("function ") + temp_function_name_length 
 		+ Z_STRLEN_PP(z_function_args)
 		+ 2 /* parentheses */
 		+ 2 /* curlies */
 		+ Z_STRLEN_PP(z_function_code);
 	eval_code = (char *) emalloc(eval_code_length);
-	sprintf(eval_code, "function " TEMP_OVRD_FUNC_NAME "(%s){%s}",
+	sprintf(eval_code, "function %s (%s){%s}",
+			temp_function_name,
 			Z_STRVAL_PP(z_function_args), Z_STRVAL_PP(z_function_code));
 	eval_name = zend_make_compiled_string_description("runtime-created override function" TSRMLS_CC);
 	retval = zend_eval_string(eval_code, NULL, eval_name TSRMLS_CC);
@@ -638,12 +647,14 @@
 	if (retval == SUCCESS) {
 		zend_function *func;
 
-		if (zend_hash_find(EG(function_table), TEMP_OVRD_FUNC_NAME,
-						   sizeof(TEMP_OVRD_FUNC_NAME), (void **) &func) == FAILURE) 
+		if (zend_hash_find(EG(function_table), temp_function_name,
+						   temp_function_name_length, (void **) &func) == FAILURE) 
 			{
 				zend_error(E_ERROR, "%s() temporary function name not present in global function_table", get_active_function_name(TSRMLS_C));
+				efree(temp_function_name);
 				RETURN_FALSE;
 			}
+		efree(temp_function_name);
 		function_add_ref(func);
 		zend_hash_del(EG(function_table), Z_STRVAL_PP(z_function_name),
 					  Z_STRLEN_PP(z_function_name) + 1);
@@ -656,6 +667,7 @@
 		RETURN_TRUE;
 	}   
 	else {
+		efree(temp_function_name);
 		RETURN_FALSE;
 	}
 }

APD hasn't had a release in 10 years, this means it's source code is way out of sync with modern PHP.

I'm going to mark this bug as suspended, the report can still be found if a maintainer for APD comes forward.

Sorry about the wait.