diff --git a/docs/notes/php.md b/docs/notes/php.md
index 85b81335a..4baf80749 100644
--- a/docs/notes/php.md
+++ b/docs/notes/php.md
@@ -284,6 +284,41 @@ confidently and wrongly*, which is the clearest single argument in
 this port for hand-answering rather than deriving: the mechanical
 method is right 90 times and this is one of the others.
 
+### And the no-atomics arm had never been compiled by anyone
+
+`zend_atomic.c:44` answered
+`argument prototype mismatch "IND STRUCT zend_atomic_bool_s" for
+"IND STRUCT zend_atomic_int_s"`. It is **upstream's typo**, not
+ours: `zend_atomic.h:323` declares
+`zend_atomic_bool_compare_exchange_ex(zend_atomic_int *obj, ...)`,
+while the other four arms -- C11, GNUC, SYNC and WIN32, at `:106`,
+`:161`, `:207`, `:263` -- all say `zend_atomic_bool *`, as does every
+sibling `_bool_` function in that same arm.
+
+***IT SURVIVES BECAUSE NOBODY COMPILES THAT ARM.*** It is reached
+only by a platform with no C11 atomics, no GCC atomics, no `__sync`
+builtins and not Windows -- which until kencc was no platform at all.
+And **gcc only warns** (`-Wincompatible-pointer-types`) where kencc
+errors, so even someone who did compile it might not have noticed.
+Fixed in the vendored source, one word, with the reasoning beside it.
+Worth reporting upstream.
+
+**The arm has exactly one bug, which is measured rather than hoped.**
+Compiling it in isolation found nothing, because the mismatch is
+between a caller and a callee and the arm is self-consistent within
+itself. Forcing `HAVE_NO_ATOMICS` in a copy of the header and
+compiling the real `zend_atomic.c` against it reproduces the kencc
+diagnostic exactly and reports **nothing else** -- and after the fix,
+nothing at all.
+
+*Forcing it took two attempts.* The first `-I` did nothing, because
+`zend_atomic.c` includes `"zend_atomic.h"` **quoted**, which resolves
+next to the source file before any `-I`; the compile silently took
+the GNUC arm and reported a clean result. **A forced configuration
+that was not actually forced reads exactly like a passing one** --
+the tell was that the `#warning` was absent, and checking for it is
+what turned a false clean into a real one.
+
 ### The atomics: not worth implementing for this build, and here is why
 
 `#warning No atomics support detected` appears on every file and is
diff --git a/sys/src/ape/cmd/php/cfg/main/php_config.h b/sys/src/ape/cmd/php/cfg/main/php_config.h
index 1dc42e87e..fab34768f 100644
--- a/sys/src/ape/cmd/php/cfg/main/php_config.h
+++ b/sys/src/ape/cmd/php/cfg/main/php_config.h
@@ -183,7 +183,7 @@
 /* #undef HAVE_DLFCN_H */
 /* #undef HAVE_LIBDL */
 
-/* absent: ODBC (14 names), tidy, linux/*, the SSE intrinsic headers,
+/* absent: ODBC (14 names), tidy, the linux/ family, the SSE headers,
  * Windows, crypt.h, sys/ipc.h, sys/mount.h, sys/statfs.h, sys/vfs.h,
  * pty.h, ieeefp.h, cpuid.h, io.h, dns.h, libproc.h, valgrind. */
 /* #undef HAVE_CRYPT_H */
diff --git a/sys/src/external/php/Zend/zend_atomic.h b/sys/src/external/php/Zend/zend_atomic.h
index 5eeb212ec..eecf329b6 100644
--- a/sys/src/external/php/Zend/zend_atomic.h
+++ b/sys/src/external/php/Zend/zend_atomic.h
@@ -320,7 +320,21 @@ static zend_always_inline void zend_atomic_int_store_ex(zend_atomic_int *obj, in
 	obj->value = desired;
 }
 
-static zend_always_inline bool zend_atomic_bool_compare_exchange_ex(zend_atomic_int *obj, bool *expected, bool desired) {
+/*
+ * APExp: `zend_atomic_int *' here was UPSTREAM'S TYPO and this is the
+ * one-word fix.  The other four arms of this file -- C11, GNUC, SYNC
+ * and WIN32, at :106, :161, :207 and :263 -- all declare
+ * `zend_atomic_bool *', as does every sibling `_bool_' function in
+ * this same arm, and `zend_atomic.c:44' passes a `zend_atomic_bool *'.
+ *
+ * ***IT SURVIVES BECAUSE NOBODY COMPILES THIS ARM.***  It is reached
+ * only when a platform has no C11 atomics, no GCC atomics, no
+ * `__sync' builtins and is not Windows, which until kencc was no
+ * platform at all.  gcc only WARNS here (`-Wincompatible-pointer-
+ * types'); kencc makes it an error, which is why APExp is the first
+ * to see it.  Worth reporting upstream.
+ */
+static zend_always_inline bool zend_atomic_bool_compare_exchange_ex(zend_atomic_bool *obj, bool *expected, bool desired) {
 	bool prev = obj->value;
 	if (prev == *expected) {
 		obj->value = desired;