List all PHP extension api version no in zend_extensions.h

Zend/zend_extensions.h

@@ -30,6 +30,25 @@
  */
 #define ZEND_EXTENSION_API_NO	320140815
 
+
+/*
+The constants below are derived from ext/opcache/ZendAccelerator.h
+
+You can use the following macro to check the extension API version for compatibilities:
+
+#if ZEND_EXTENSION_API_NO < ZEND_EXTENSION_API_NO_5_5_X
+   // do something for php versions lower than 5.5.x
+#endif
+*/
+#define ZEND_EXTENSION_API_NO_5_0_X 220040412
+#define ZEND_EXTENSION_API_NO_5_1_X 220051025
+#define ZEND_EXTENSION_API_NO_5_2_X 220060519
+#define ZEND_EXTENSION_API_NO_5_3_X 220090626
+#define ZEND_EXTENSION_API_NO_5_4_X 220100525
+#define ZEND_EXTENSION_API_NO_5_5_X 220121212
+#define ZEND_EXTENSION_API_NO_5_6_X 220131226
+#define ZEND_EXTENSION_API_NO_7_1_X 320140815
+
 typedef struct _zend_extension_version_info {
 	int zend_extension_api_no;
 	char *build_id;