diff --git a/build/php.m4 b/build/php.m4
index e82e856667e..0a2169f6f51 100644
--- a/build/php.m4
+++ b/build/php.m4
@@ -2502,3 +2502,43 @@ AC_DEFUN([PHP_REMOVE_OPTIMIZATION_FLAGS], [
   CFLAGS=$(echo "$CFLAGS" | $SED -e "$sed_script")
   CXXFLAGS=$(echo "$CXXFLAGS" | $SED -e "$sed_script")
 ])
+
+dnl
+dnl PHP_C_STANDARD_LIBRARY
+dnl
+dnl Determine the C standard library used for the build. The uclibc is checked
+dnl first because it also defines the __GLIBC__ and could otherwise be detected
+dnl as glibc. Musl C library is determined heuristically.
+dnl
+AC_DEFUN([PHP_C_STANDARD_LIBRARY],
+[AC_CACHE_CHECK([C standard library implementation],
+[php_cv_c_standard_library],
+[php_cv_c_standard_library=unknown
+dnl Check if C standard library is uclibc.
+AS_VAR_IF([php_cv_c_standard_library], [unknown],
+[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <features.h>],
+[#ifndef __UCLIBC__
+  (void) __UCLIBC__;
+#endif])],
+[php_cv_c_standard_library=uclibc],
+[php_cv_c_standard_library=unknown])])
+dnl Check if C standard library is GNU C.
+AS_VAR_IF([php_cv_c_standard_library], [unknown],
+[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <features.h>],
+[#ifndef __GLIBC__
+  (void) __GLIBC__;
+#endif])],
+[php_cv_c_standard_library=glibc],
+[php_cv_c_standard_library=unknown])])
+dnl Check if C standard library is musl libc.
+AS_VAR_IF([php_cv_c_standard_library], [unknown],
+[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <stdarg.h>],
+[#ifndef __DEFINED_va_list
+  (void) __DEFINED_va_list;
+#endif])],
+[php_cv_c_standard_library=musl],
+[AS_IF([command -v ldd >/dev/null && ldd --version 2>&1 | grep ^musl >/dev/null 2>&1],
+[php_cv_c_standard_library=musl],
+[php_cv_c_standard_library=unknown])])])
+])
+])
diff --git a/configure.ac b/configure.ac
index 54f6157d96a..86b5b071639 100644
--- a/configure.ac
+++ b/configure.ac
@@ -250,15 +250,10 @@ case $host_alias in
     ;;
 esac
 
-dnl Detect musl libc
-AC_MSG_CHECKING([whether we are using musl libc])
-if command -v ldd >/dev/null && ldd --version 2>&1 | grep ^musl >/dev/null 2>&1
-then
-  AC_MSG_RESULT([yes])
-  AC_DEFINE([__MUSL__], [1], [Define to 1 when using musl libc.])
-else
-  AC_MSG_RESULT([no])
-fi
+dnl Detect C library.
+PHP_C_STANDARD_LIBRARY
+AS_VAR_IF([php_cv_c_standard_library], [musl],
+  [AC_DEFINE([__MUSL__], [1], [Define when using musl libc.])])
 
 dnl Add _GNU_SOURCE compile definition because the php_config.h with definitions
 dnl by AC_USE_SYSTEM_EXTENSIONS might be included after the system headers which
diff --git a/ext/posix/config.m4 b/ext/posix/config.m4
index 8960979065f..86554635695 100644
--- a/ext/posix/config.m4
+++ b/ext/posix/config.m4
@@ -44,7 +44,8 @@ if test "$PHP_POSIX" = "yes"; then
 
 dnl Skip pathconf and fpathconf check on musl libc due to limited implementation
 dnl (first argument is not validated and has different error).
-  AS_IF([command -v ldd >/dev/null && ldd --version 2>&1 | grep ^musl >/dev/null 2>&1],
+  PHP_C_STANDARD_LIBRARY
+  AS_VAR_IF([php_cv_c_standard_library], [musl],
     [],
     [AC_CHECK_FUNCS([pathconf fpathconf])])