diff --git a/ext/date/config.w32 b/ext/date/config.w32
index 23af2f7d65871..b053e27aae354 100644
--- a/ext/date/config.w32
+++ b/ext/date/config.w32
@@ -20,4 +20,4 @@ tl_config.WriteLine("#define timelib_free    efree");
 tl_config.Close();
 
 PHP_INSTALL_HEADERS("ext/date", "php_date.h lib/timelib.h lib/timelib_config.h");
-AC_DEFINE('HAVE_TIMELIB_CONFIG_H', 1, 'Have timelib_config.h')
+AC_DEFINE('HAVE_TIMELIB_CONFIG_H', 1, 'Define to 1 if you have the <timelib_config.h> header file.');
diff --git a/ext/date/config0.m4 b/ext/date/config0.m4
index 1f091215be3ed..5af6be13faf71 100644
--- a/ext/date/config0.m4
+++ b/ext/date/config0.m4
@@ -22,7 +22,8 @@ PHP_ADD_INCLUDE([$ext_builddir/lib])
 PHP_ADD_INCLUDE([$ext_srcdir/lib])
 
 PHP_INSTALL_HEADERS([ext/date], [php_date.h lib/timelib.h lib/timelib_config.h])
-AC_DEFINE([HAVE_TIMELIB_CONFIG_H], [1], [Have timelib_config.h])
+AC_DEFINE([HAVE_TIMELIB_CONFIG_H], [1],
+  [Define to 1 if you have the <timelib_config.h> header file.])
 
 cat > $ext_builddir/lib/timelib_config.h <<EOF
 #ifdef PHP_WIN32
diff --git a/ext/hash/config.m4 b/ext/hash/config.m4
index de449149a0c27..f5608183504ea 100644
--- a/ext/hash/config.m4
+++ b/ext/hash/config.m4
@@ -5,12 +5,13 @@ PHP_ARG_WITH([mhash],
 
 if test "$PHP_MHASH" != "no"; then
   AC_MSG_WARN([The --with-mhash option and mhash* functions are deprecated as of PHP 8.1.0])
-  AC_DEFINE(PHP_MHASH_BC, 1, [ ])
+  AC_DEFINE([PHP_MHASH_BC], [1], [Define to 1 if mhash support is enabled.])
 fi
 
 if test $ac_cv_c_bigendian_php = yes; then
   EXT_HASH_SHA3_SOURCES="hash_sha3.c"
-  AC_DEFINE(HAVE_SLOW_HASH3, 1, [Define if hash3 algo is available])
+  AC_DEFINE([HAVE_SLOW_HASH3], [1],
+    [Define to 1 if the PHP hash extension uses the slow SHA3 algorithm.])
   AC_MSG_WARN([Using SHA3 slow implementation on bigendian])
   SHA3_DIR=
 else
diff --git a/ext/hash/config.w32 b/ext/hash/config.w32
index 09f0ad2453fa9..e574026ac0d3b 100644
--- a/ext/hash/config.w32
+++ b/ext/hash/config.w32
@@ -4,7 +4,7 @@ ARG_WITH('mhash', 'mhash support (BC via hash)', 'no');
 
 if (PHP_MHASH != 'no') {
 	WARNING("mhash* functions are deprecated as of PHP 8.1.0");
-	AC_DEFINE('PHP_MHASH_BC', 1);
+	AC_DEFINE('PHP_MHASH_BC', 1, 'Define to 1 if mhash support is enabled.');
 }
 
 PHP_HASH = 'yes';
diff --git a/ext/mbstring/config.m4 b/ext/mbstring/config.m4
index c2f1fe5fea7cf..b97fbd4ded7aa 100644
--- a/ext/mbstring/config.m4
+++ b/ext/mbstring/config.m4
@@ -75,7 +75,8 @@ AC_DEFUN([PHP_MBSTRING_SETUP_MBREGEX], [
     PHP_MBSTRING_ADD_CFLAG([-DONIG_ESCAPE_UCHAR_COLLISION=1])
     PHP_MBSTRING_ADD_CFLAG([-DUChar=OnigUChar])
 
-    AC_DEFINE([HAVE_MBREGEX], 1, [whether to have multibyte regex support])
+    AC_DEFINE([HAVE_MBREGEX], [1],
+      [Define to 1 if mbstring has multibyte regex support enabled.])
 
     PHP_MBSTRING_ADD_BASE_SOURCES([php_mbregex.c])
     PHP_INSTALL_HEADERS([ext/mbstring], [php_mbregex.h php_onig_compat.h])
diff --git a/ext/mbstring/config.w32 b/ext/mbstring/config.w32
index dbfd1086488a3..37c01b84fd1e2 100644
--- a/ext/mbstring/config.w32
+++ b/ext/mbstring/config.w32
@@ -43,7 +43,7 @@ if (PHP_MBSTRING != "no") {
 		if (PHP_MBREGEX != "no") {
 			if (CHECK_HEADER_ADD_INCLUDE("oniguruma.h", "CFLAGS_MBSTRING", PHP_MBREGEX) &&
 				CHECK_LIB("onig_a.lib;libonig_a.lib", "mbstring", PHP_MBSTRING)) {
-				AC_DEFINE('HAVE_MBREGEX', 1);
+				AC_DEFINE('HAVE_MBREGEX', 1, 'Define to 1 if mbstring has multibyte regex support enabled.');
 
 				/* XXX libonig is only usable as a static library ATM, code change required to link with a DLL. */
 				ADD_FLAG("CFLAGS_MBSTRING", "/DONIG_EXTERN=extern /DPHP_ONIG_BAD_KOI8_ENTRY=1 /utf-8");
diff --git a/ext/opcache/config.m4 b/ext/opcache/config.m4
index 5e1a496a56819..01f5169299df4 100644
--- a/ext/opcache/config.m4
+++ b/ext/opcache/config.m4
@@ -30,9 +30,9 @@ if test "$PHP_OPCACHE" != "no"; then
   dnl Always build as shared extension
   ext_shared=yes
 
-  if test "$PHP_HUGE_CODE_PAGES" = "yes"; then
-    AC_DEFINE(HAVE_HUGE_CODE_PAGES, 1, [Define to enable copying PHP CODE pages into HUGE PAGES (experimental)])
-  fi
+  AS_VAR_IF([PHP_HUGE_CODE_PAGES], [yes],
+    [AC_DEFINE([HAVE_HUGE_CODE_PAGES], [1],
+      [Define to 1 to enable copying PHP CODE pages into HUGE PAGES.])])
 
   if test "$PHP_OPCACHE_JIT" = "yes"; then
     case $host_cpu in
@@ -50,7 +50,7 @@ if test "$PHP_OPCACHE" != "no"; then
   fi
 
   if test "$PHP_OPCACHE_JIT" = "yes" ; then
-    AC_DEFINE(HAVE_JIT, 1, [Define to enable JIT])
+    AC_DEFINE([HAVE_JIT], [1], [Define to 1 to enable JIT.])
     ZEND_JIT_SRC=m4_normalize(["
       jit/ir/ir_cfg.c
       jit/ir/ir_check.c
diff --git a/ext/opcache/config.w32 b/ext/opcache/config.w32
index 9c15e52f6f326..0d498ab776891 100644
--- a/ext/opcache/config.w32
+++ b/ext/opcache/config.w32
@@ -32,7 +32,7 @@ if (PHP_OPCACHE != "no") {
 			DEFINE("DASM_FLAGS", dasm_flags);
 			DEFINE("DASM_ARCH", "x86");
 
-			AC_DEFINE('HAVE_JIT', 1, 'Define to enable JIT');
+			AC_DEFINE('HAVE_JIT', 1, 'Define to 1 to enable JIT.');
 
 			ADD_FLAG("CFLAGS_OPCACHE", "/I \"ext\\opcache\\jit\\ir\" /D "+ir_target+" /D IR_PHP");
 			if (PHP_DEBUG == "yes") {
diff --git a/ext/openssl/config0.m4 b/ext/openssl/config0.m4
index 213efc79572ba..e80281110ffe0 100644
--- a/ext/openssl/config0.m4
+++ b/ext/openssl/config0.m4
@@ -29,11 +29,13 @@ if test "$PHP_OPENSSL" != "no"; then
       [Define to 1 if OpenSSL crypto library has the 'RAND_egd' function.])],,
     [$OPENSSL_LIBS])
 
-  if test "$PHP_SYSTEM_CIPHERS" != "no"; then
-    AC_DEFINE(USE_OPENSSL_SYSTEM_CIPHERS,1,[ Use system default cipher list instead of hardcoded value ])
-  fi
+  AS_VAR_IF([PHP_SYSTEM_CIPHERS], [no],,
+    [AC_DEFINE([USE_OPENSSL_SYSTEM_CIPHERS], [1],
+      [Define to 1 to use system default cipher list instead of the hardcoded
+      value in OpenSSL.])])
 
-  if test "$PHP_OPENSSL_LEGACY_PROVIDER" != "no"; then
-    AC_DEFINE(LOAD_OPENSSL_LEGACY_PROVIDER,1,[ Load legacy algorithm provider in addition to default provider ])
-  fi
+  AS_VAR_IF([PHP_OPENSSL_LEGACY_PROVIDER], [no],,
+    [AC_DEFINE([LOAD_OPENSSL_LEGACY_PROVIDER], [1],
+      [Define to 1 to load the OpenSSL legacy algorithm provider in addition to
+      the default provider.])])
 fi
diff --git a/ext/pcntl/config.m4 b/ext/pcntl/config.m4
index 8a4a10d85e8b8..3476b5065cef5 100644
--- a/ext/pcntl/config.m4
+++ b/ext/pcntl/config.m4
@@ -49,7 +49,8 @@ int main(void) {
   [php_cv_func_sched_getcpu=no],
   [php_cv_func_sched_getcpu=no])])
   AS_VAR_IF([php_cv_func_sched_getcpu], [yes],
-    [AC_DEFINE([HAVE_SCHED_GETCPU], [1], [Whether sched_getcpu is properly supported])])
+    [AC_DEFINE([HAVE_SCHED_GETCPU], [1],
+      [Define to 1 if the 'sched_getcpu' function is properly supported.])])
 
   AC_CHECK_TYPE([siginfo_t],[PCNTL_CFLAGS="-DHAVE_STRUCT_SIGINFO_T"],,[#include <signal.h>])
 
diff --git a/ext/posix/config.m4 b/ext/posix/config.m4
index b5c45dd1c899e..ac70068bac8f6 100644
--- a/ext/posix/config.m4
+++ b/ext/posix/config.m4
@@ -58,7 +58,7 @@ dnl (first argument is not validated and has different error).
       [php_cv_func_ttyname_r=yes], [php_cv_func_ttyname_r=no])])])
   AS_VAR_IF([php_cv_func_ttyname_r], [yes],
     [AC_DEFINE([HAVE_TTYNAME_R], [1],
-      [Define to 1 if you have a working ttyname_r.])],
+      [Define to 1 if you have a working 'ttyname_r' function.])],
     [AC_MSG_NOTICE([posix_ttyname() will be thread-unsafe])])
 
   AC_CHECK_MEMBERS([struct utsname.domainname],,,[
diff --git a/ext/session/config.m4 b/ext/session/config.m4
index 3bdab7de1c4c1..c3121b2f03dea 100644
--- a/ext/session/config.m4
+++ b/ext/session/config.m4
@@ -45,5 +45,5 @@ if test "$PHP_MM" != "no"; then
     [SESSION_SHARED_LIBADD])
   PHP_ADD_INCLUDE([$MM_DIR/include])
   PHP_INSTALL_HEADERS([ext/session], [mod_mm.h])
-  AC_DEFINE(HAVE_LIBMM, 1, [Whether you have libmm])
+  AC_DEFINE([HAVE_LIBMM], [1], [Define to 1 if the system has the 'mm' library.])
 fi
diff --git a/ext/standard/config.m4 b/ext/standard/config.m4
index dc5dc1b472b48..b3e3e975a8172 100644
--- a/ext/standard/config.m4
+++ b/ext/standard/config.m4
@@ -324,9 +324,9 @@ case "$PHP_SAPI" in
   ;;
 esac
 
-if test "$PHP_ENABLE_CHROOT_FUNC" = "yes"; then
-  AC_DEFINE(ENABLE_CHROOT_FUNC, 1, [Whether to enable chroot() function])
-fi
+AS_VAR_IF([PHP_ENABLE_CHROOT_FUNC], [yes],
+  [AC_DEFINE([ENABLE_CHROOT_FUNC], [1],
+    [Define to 1 to enable the 'chroot' function.])])
 
 dnl
 dnl Detect library functions needed by php dns_xxx functions
@@ -370,7 +370,8 @@ if test "$PHP_PASSWORD_ARGON2" != "no"; then
   PHP_EVAL_INCLINE([$ARGON2_CFLAGS])
   PHP_EVAL_LIBLINE([$ARGON2_LIBS])
 
-  AC_DEFINE(HAVE_ARGON2LIB, 1, [ ])
+  AC_DEFINE([HAVE_ARGON2LIB], [1],
+    [Define to 1 if the system has the 'libargon2' library.])
 fi
 
 dnl
diff --git a/ext/standard/config.w32 b/ext/standard/config.w32
index 282189c52dade..4740b6930ce9d 100644
--- a/ext/standard/config.w32
+++ b/ext/standard/config.w32
@@ -8,7 +8,7 @@ if (PHP_PASSWORD_ARGON2 != "no") {
 		if (!CHECK_FUNC_IN_HEADER("argon2.h", "argon2id_hash_raw", PHP_PHP_BUILD + "\\include", "CFLAGS")) {
 			ERROR("Please verify that Argon2 header and libraries >= 20161029 are installed");
 		}
-		AC_DEFINE('HAVE_ARGON2LIB', 1);
+		AC_DEFINE('HAVE_ARGON2LIB', 1, "Define to 1 if the system has the 'libargon2' library.");
 	} else {
 		WARNING("Argon2 not enabled; libraries and headers not found");
 	}
diff --git a/ext/xsl/config.m4 b/ext/xsl/config.m4
index 9f0bbe021a2d9..c7e59bc4074f8 100644
--- a/ext/xsl/config.m4
+++ b/ext/xsl/config.m4
@@ -23,7 +23,7 @@ if test "$PHP_XSL" != "no"; then
     PHP_EVAL_INCLINE([$EXSLT_CFLAGS])
     PHP_EVAL_LIBLINE([$EXSLT_LIBS], [XSL_SHARED_LIBADD])
     AC_DEFINE([HAVE_XSL_EXSLT], [1],
-      [Define to 1 if system has the EXSLT extension library for XSLT.])
+      [Define to 1 if the system has the EXSLT extension library for XSLT.])
   ], [ ])
 
   AC_DEFINE([HAVE_XSL], [1],
diff --git a/ext/xsl/config.w32 b/ext/xsl/config.w32
index fadf7ced01d7c..4990c3c5bd073 100644
--- a/ext/xsl/config.w32
+++ b/ext/xsl/config.w32
@@ -28,7 +28,7 @@ if (PHP_XSL != "no") {
 		if (ext_xsl_lib_found && CHECK_HEADER_ADD_INCLUDE("libxslt\\xslt.h", "CFLAGS_XSL")) {
 			if (ext_exslt_lib_found) {
 				if (CHECK_HEADER_ADD_INCLUDE("libexslt\\exslt.h", "CFLAGS_XSL")) {
-					AC_DEFINE("HAVE_XSL_EXSLT", 1, "Define to 1 if system has the EXSLT extension library for XSLT.");
+					AC_DEFINE("HAVE_XSL_EXSLT", 1, "Define to 1 if the system has the EXSLT extension library for XSLT.");
 				}
 			}
 			EXTENSION("xsl", "php_xsl.c xsltprocessor.c", PHP_XSL_SHARED);
diff --git a/sapi/cgi/config9.m4 b/sapi/cgi/config9.m4
index 15fca6e34a3bf..eaae5f7441084 100644
--- a/sapi/cgi/config9.m4
+++ b/sapi/cgi/config9.m4
@@ -14,7 +14,7 @@ if test "$PHP_CGI" != "no"; then
       SunOS\ 5.*)
         AC_MSG_RESULT([yes])
         AC_DEFINE([USE_LOCKING], [1],
-          [Define if cross-process locking is required by accept()])
+          [Define to 1 if cross-process locking is required by 'accept()'.])
       ;;
       *)
         AC_MSG_RESULT([no])
diff --git a/sapi/phpdbg/config.m4 b/sapi/phpdbg/config.m4
index b65fc940ee1f7..936a2c96f9206 100644
--- a/sapi/phpdbg/config.m4
+++ b/sapi/phpdbg/config.m4
@@ -32,7 +32,8 @@ if test "$PHP_PHPDBG" != "no"; then
   AC_MSG_CHECKING([for phpdbg and readline integration])
   if test "$PHP_PHPDBG_READLINE" = "yes"; then
     if test "$PHP_READLINE" != "no" || test "$PHP_LIBEDIT" != "no"; then
-      AC_DEFINE(HAVE_PHPDBG_READLINE, 1, [ ])
+      AC_DEFINE([HAVE_PHPDBG_READLINE], [1],
+        [Define to 1 if the phpdbg SAPI has libedit/readline integration.])
       PHPDBG_EXTRA_LIBS="$PHP_READLINE_LIBS"
       AC_MSG_RESULT([ok])
     else