diff --git a/TSRM/TSRM.c b/TSRM/TSRM.c
index 81136bee4daa9..f4179bc389157 100644
--- a/TSRM/TSRM.c
+++ b/TSRM/TSRM.c
@@ -60,7 +60,7 @@ static size_t tsrm_reserved_pos  = 0;
 static size_t tsrm_reserved_size = 0;
 
 static MUTEX_T tsmm_mutex;	  /* thread-safe memory manager mutex */
-static MUTEX_T tsrm_env_mutex; /* tsrm environ mutex */
+static RWLOCK_T tsrm_env_mutex; /* tsrm environ mutex */
 
 /* New thread handlers */
 static tsrm_thread_begin_func_t tsrm_new_thread_begin_handler = NULL;
@@ -156,7 +156,7 @@ TSRM_API bool tsrm_startup(int expected_threads, int expected_resources, int deb
 	tsrm_reserved_pos  = 0;
 	tsrm_reserved_size = 0;
 
-	tsrm_env_mutex = tsrm_mutex_alloc();
+	tsrm_env_mutex = tsrm_rwlock_alloc();
 
 	return 1;
 }/*}}}*/
@@ -212,7 +212,7 @@ TSRM_API void tsrm_shutdown(void)
 	free(tsrm_tls_table);
 	free(resource_types_table);
 	tsrm_mutex_free(tsmm_mutex);
-	tsrm_mutex_free(tsrm_env_mutex);
+	tsrm_rwlock_free(tsrm_env_mutex);
 	TSRM_ERROR((TSRM_ERROR_LEVEL_CORE, "Shutdown TSRM"));
 	if (tsrm_error_file!=stderr) {
 		fclose(tsrm_error_file);
@@ -236,12 +236,20 @@ TSRM_API void tsrm_shutdown(void)
 
 /* {{{ */
 /* environ lock api */
-TSRM_API void tsrm_env_lock(void) {
-	tsrm_mutex_lock(tsrm_env_mutex);
+TSRM_API void tsrm_env_lock(bool write) {
+	if (write) {
+		tsrm_rwlock_wrlock(tsrm_env_mutex);
+	} else {
+		tsrm_rwlock_rlock(tsrm_env_mutex);
+	}
 }
 
-TSRM_API void tsrm_env_unlock(void) {
-	tsrm_mutex_unlock(tsrm_env_mutex);
+TSRM_API void tsrm_env_unlock(bool write) {
+	if (write) {
+		tsrm_rwlock_wrunlock(tsrm_env_mutex);
+	} else {
+		tsrm_rwlock_runlock(tsrm_env_mutex);
+	}
 } /* }}} */
 
 /* enlarge the arrays for the already active threads */
@@ -648,6 +656,47 @@ TSRM_API void tsrm_mutex_free(MUTEX_T mutexp)
 #endif
 }/*}}}*/
 
+/* Allocate a read-write lock */
+TSRM_API RWLOCK_T tsrm_rwlock_alloc(void)
+{/*{{{*/
+    RWLOCK_T rwlock;
+#ifdef TSRM_WIN32
+    rwlock = malloc(sizeof(SRWLOCK));
+    if (!rwlock) {
+        fprintf(stderr, "Failed to allocate SRWLOCK\n");
+        return NULL;
+    }
+    InitializeSRWLock(rwlock);
+#else
+    rwlock = (pthread_rwlock_t *)malloc(sizeof(pthread_rwlock_t));
+    if (!rwlock) {
+        fprintf(stderr, "Failed to allocate pthread_rwlock_t\n");
+        return NULL;
+    }
+    pthread_rwlock_init(rwlock, NULL);
+#endif
+#ifdef THR_DEBUG
+    printf("Read-Write Lock created thread: %d\n", mythreadid());
+#endif
+    return rwlock;
+}/*}}}*/
+
+/* Free a read-write lock */
+TSRM_API void tsrm_rwlock_free(RWLOCK_T rwlock)
+{/*{{{*/
+    if (rwlock) {
+#ifdef TSRM_WIN32
+        // No explicit free function for SRWLOCK, but we still free the memory.
+        free(rwlock);
+#else
+        pthread_rwlock_destroy(rwlock);
+        free(rwlock);
+#endif
+    }
+#ifdef THR_DEBUG
+    printf("Read-Write Lock freed thread: %d\n", mythreadid());
+#endif
+}/*}}}*/
 
 /*
   Lock a mutex.
@@ -664,6 +713,65 @@ TSRM_API int tsrm_mutex_lock(MUTEX_T mutexp)
 #endif
 }/*}}}*/
 
+/*
+  Lock a mutex for writing.
+  A return value of 0 indicates success
+*/
+TSRM_API int tsrm_rwlock_wrlock(RWLOCK_T rwlock)
+{/*{{{*/
+	TSRM_ERROR((TSRM_ERROR_LEVEL_INFO, "Write locked thread: %ld", tsrm_thread_id()));
+#ifdef TSRM_WIN32
+	AcquireSRWLockExclusive(rwlock);
+	return 0;
+#else
+	return pthread_rwlock_wrlock(rwlock);
+#endif
+}/*}}}*/
+
+/*
+  Lock a mutex for reading.
+  A return value of 0 indicates success
+*/
+TSRM_API int tsrm_rwlock_rlock(RWLOCK_T rwlock)
+{/*{{{*/
+	TSRM_ERROR((TSRM_ERROR_LEVEL_INFO, "Read locked thread: %ld", tsrm_thread_id()));
+#ifdef TSRM_WIN32
+	AcquireSRWLockShared(rwlock);
+	return 0;
+#else
+	return pthread_rwlock_rdlock(rwlock);
+#endif
+}/*}}}*/
+
+/*
+  Unlock a mutex for reading.
+  A return value of 0 indicates success
+*/
+TSRM_API int tsrm_rwlock_runlock(RWLOCK_T rwlock)
+{/*{{{*/
+	TSRM_ERROR((TSRM_ERROR_LEVEL_INFO, "Read unlocked thread: %ld", tsrm_thread_id()));
+#ifdef TSRM_WIN32
+	ReleaseSRWLockShared(rwlock);
+	return 0;
+#else
+	return pthread_rwlock_unlock(rwlock);
+#endif
+}/*}}}*/
+
+/*
+  Unlock a mutex for writing.
+  A return value of 0 indicates success
+*/
+TSRM_API int tsrm_rwlock_wrunlock(RWLOCK_T rwlock)
+{/*{{{*/
+	TSRM_ERROR((TSRM_ERROR_LEVEL_INFO, "Write unlocked thread: %ld", tsrm_thread_id()));
+#ifdef TSRM_WIN32
+	ReleaseSRWLockExclusive(rwlock);
+	return 0;
+#else
+	return pthread_rwlock_unlock(rwlock);
+#endif
+}/*}}}*/
 
 /*
   Unlock a mutex.
diff --git a/TSRM/TSRM.h b/TSRM/TSRM.h
index 80d6cbad04435..6dc53291c0e33 100644
--- a/TSRM/TSRM.h
+++ b/TSRM/TSRM.h
@@ -63,9 +63,11 @@ typedef int ts_rsrc_id;
 #ifdef TSRM_WIN32
 # define THREAD_T DWORD
 # define MUTEX_T CRITICAL_SECTION *
+# define RWLOCK_T SRWLOCK *
 #else
 # define THREAD_T pthread_t
 # define MUTEX_T pthread_mutex_t *
+# define RWLOCK_T pthread_rwlock_t *
 #endif
 
 #include <signal.h>
@@ -84,8 +86,8 @@ TSRM_API bool tsrm_startup(int expected_threads, int expected_resources, int deb
 TSRM_API void tsrm_shutdown(void);
 
 /* environ lock API */
-TSRM_API void tsrm_env_lock(void);
-TSRM_API void tsrm_env_unlock(void);
+TSRM_API void tsrm_env_lock(bool write);
+TSRM_API void tsrm_env_unlock(bool write);
 
 /* allocates a new thread-safe-resource id */
 TSRM_API ts_rsrc_id ts_allocate_id(ts_rsrc_id *rsrc_id, size_t size, ts_allocate_ctor ctor, ts_allocate_dtor dtor);
@@ -125,8 +127,14 @@ TSRM_API void tsrm_error_set(int level, const char *debug_filename);
 TSRM_API THREAD_T tsrm_thread_id(void);
 TSRM_API MUTEX_T tsrm_mutex_alloc(void);
 TSRM_API void tsrm_mutex_free(MUTEX_T mutexp);
+TSRM_API RWLOCK_T tsrm_rwlock_alloc(void);
+TSRM_API void tsrm_rwlock_free(RWLOCK_T rwlock);
 TSRM_API int tsrm_mutex_lock(MUTEX_T mutexp);
 TSRM_API int tsrm_mutex_unlock(MUTEX_T mutexp);
+TSRM_API int tsrm_rwlock_wrlock(RWLOCK_T rwlock);
+TSRM_API int tsrm_rwlock_wrunlock(RWLOCK_T rwlock);
+TSRM_API int tsrm_rwlock_rlock(RWLOCK_T rwlock);
+TSRM_API int tsrm_rwlock_runlock(RWLOCK_T rwlock);
 #ifdef HAVE_SIGPROCMASK
 TSRM_API int tsrm_sigmask(int how, const sigset_t *set, sigset_t *oldset);
 #endif
@@ -188,8 +196,8 @@ TSRM_API bool tsrm_is_managed_thread(void);
 
 #else /* non ZTS */
 
-#define tsrm_env_lock()
-#define tsrm_env_unlock()
+#define tsrm_env_lock(write)
+#define tsrm_env_unlock(write)
 
 #define TSRMG_STATIC(id, type, element)
 #define TSRMLS_MAIN_CACHE_EXTERN()
diff --git a/ext/standard/basic_functions.c b/ext/standard/basic_functions.c
index dbbf9896f2b73..0933a866121cc 100644
--- a/ext/standard/basic_functions.c
+++ b/ext/standard/basic_functions.c
@@ -448,9 +448,9 @@ PHP_RSHUTDOWN_FUNCTION(basic) /* {{{ */
 		BG(strtok_string) = NULL;
 	}
 #ifdef HAVE_PUTENV
-	tsrm_env_lock();
+	tsrm_env_lock(true);
 	zend_hash_destroy(&BG(putenv_ht));
-	tsrm_env_unlock();
+	tsrm_env_unlock(true);
 #endif
 
 	if (BG(umask) != -1) {
@@ -687,7 +687,7 @@ PHPAPI zend_string *php_getenv(const char *str, size_t str_len) {
 		}
 	}
 #else
-	tsrm_env_lock();
+	tsrm_env_lock(false);
 
 	/* system method returns a const */
 	char *ptr = getenv(str);
@@ -696,7 +696,7 @@ PHPAPI zend_string *php_getenv(const char *str, size_t str_len) {
 		result = zend_string_init(ptr, strlen(ptr), 0);
 	}
 
-	tsrm_env_unlock();
+	tsrm_env_unlock(false);
 	return result;
 #endif
 }
@@ -772,7 +772,7 @@ PHP_FUNCTION(putenv)
 		pe.key = zend_string_init(setting, setting_len, 0);
 	}
 
-	tsrm_env_lock();
+	tsrm_env_lock(true);
 	zend_hash_del(&BG(putenv_ht), pe.key);
 
 	/* find previous value */
@@ -807,7 +807,7 @@ PHP_FUNCTION(putenv)
 		}
 		/* valw may be NULL, but the failed conversion still needs to be checked. */
 		if (!keyw || !valw && value) {
-			tsrm_env_unlock();
+			tsrm_env_unlock(true);
 			free(pe.putenv_string);
 			zend_string_release(pe.key);
 			free(keyw);
@@ -835,7 +835,7 @@ PHP_FUNCTION(putenv)
 			tzset();
 		}
 #endif
-		tsrm_env_unlock();
+		tsrm_env_unlock(true);
 #ifdef PHP_WIN32
 		free(keyw);
 		free(valw);
diff --git a/ext/standard/info.c b/ext/standard/info.c
index 8a706ef62eb57..50ca43dd93dd0 100644
--- a/ext/standard/info.c
+++ b/ext/standard/info.c
@@ -968,7 +968,7 @@ PHPAPI ZEND_COLD void php_print_info(int flag)
 		SECTION("Environment");
 		php_info_print_table_start();
 		php_info_print_table_header(2, "Variable", "Value");
-		tsrm_env_lock();
+		tsrm_env_lock(false);
 		for (env=environ; env!=NULL && *env !=NULL; env++) {
 			tmp1 = estrdup(*env);
 			if (!(tmp2=strchr(tmp1,'='))) { /* malformed entry? */
@@ -980,7 +980,7 @@ PHPAPI ZEND_COLD void php_print_info(int flag)
 			php_info_print_table_row(2, tmp1, tmp2);
 			efree(tmp1);
 		}
-		tsrm_env_unlock();
+		tsrm_env_unlock(false);
 		php_info_print_table_end();
 	}
 
diff --git a/main/php_variables.c b/main/php_variables.c
index 7569fd43e900c..1110c0e6eb1d6 100644
--- a/main/php_variables.c
+++ b/main/php_variables.c
@@ -628,7 +628,7 @@ static zend_always_inline void import_environment_variable(HashTable *ht, char *
 
 static void _php_import_environment_variables(zval *array_ptr)
 {
-	tsrm_env_lock();
+	tsrm_env_lock(false);
 
 #ifndef PHP_WIN32
 	for (char **env = environ; env != NULL && *env != NULL; env++) {
@@ -646,7 +646,7 @@ static void _php_import_environment_variables(zval *array_ptr)
 	FreeEnvironmentStringsW(environmentw);
 #endif
 
-	tsrm_env_unlock();
+	tsrm_env_unlock(false);
 }
 
 static void _php_load_environment_variables(zval *array_ptr)
diff --git a/sapi/litespeed/lsapi_main.c b/sapi/litespeed/lsapi_main.c
index 259d4a985cc66..abaa164cdf489 100644
--- a/sapi/litespeed/lsapi_main.c
+++ b/sapi/litespeed/lsapi_main.c
@@ -234,7 +234,7 @@ static void litespeed_php_import_environment_variables(zval *array_ptr)
         return;
     }
 
-    tsrm_env_lock();
+    tsrm_env_lock(false);
     for (env = environ; env != NULL && *env != NULL; env++) {
         p = strchr(*env, '=');
         if (!p) {               /* malformed entry? */
@@ -249,7 +249,7 @@ static void litespeed_php_import_environment_variables(zval *array_ptr)
         t[nlen] = '\0';
         add_variable(t, nlen, p + 1, strlen( p + 1 ), array_ptr);
     }
-    tsrm_env_unlock();
+    tsrm_env_unlock(false);
     if (t != buf && t != NULL) {
         efree(t);
     }