Allow for subscribe callback to return any value

This commit changes the behaviour of the various subscribe flavors
such that the callback can break the loop by returning any non-null
value.

This would allow, for example, context to be retreived from the message
and then used in such a way to return it to the caller.

Author: michael-grunder

README.markdown

@@ -2898,7 +2898,7 @@ _**Description**_: Subscribe to channels by pattern
 ##### *Parameters*
 *patterns*: An array of patterns to match
 *callback*: Either a string or an array with an object and method.  The callback will get four arguments ($redis, $pattern, $channel, $message)
-
+*return value*: Mixed.  Any non-null return value in the callback will be returned to the caller.
 ##### *Example*
 ~~~
 function psubscribe($redis, $pattern, $chan, $msg) {
@@ -2928,7 +2928,7 @@ _**Description**_: Subscribe to channels. Warning: this function will probably c
 ##### *Parameters*
 *channels*: an array of channels to subscribe to  
 *callback*: either a string or an array($instance, 'method_name'). The callback function receives 3 parameters: the redis instance, the channel name, and the message.  
-
+*return value*:  Mixed.  Any non-null return value in the callback will be returned to the caller.
 ##### *Example*
 ~~~
 function f($redis, $chan, $msg) {

redis.c

@@ -5764,21 +5764,19 @@ PHP_REDIS_API void generic_subscribe_cmd(INTERNAL_FUNCTION_PARAMETERS, char *sub
 			break;
 		}
 
-        /* Free our return value if we have one.  If the return value is a bool
-         * that is FALSE, break our subscribe loop and return control to the
-         * userland code */
-		if (z_ret) {
-			if(Z_TYPE_P(z_ret) == IS_BOOL && Z_BVAL_P(z_ret) == 0) {
-                zval_ptr_dtor(&z_ret);
-				zval_dtor(z_tab);
-				efree(z_tab);
-				break;
-			}
+        /* Free reply from Redis */
+        zval_dtor(z_tab);
+        efree(z_tab);        
+
+        /* Check for a non-null return value.  If we have one, return it from
+         * the subscribe function itself.  Otherwise continue our loop. */
+        if (z_ret) {
+            if (Z_TYPE_P(z_ret) != IS_NULL) {
+                RETVAL_ZVAL(z_ret, 0, 1);
+                break;
+            }
             zval_ptr_dtor(&z_ret);
-		}
-
-		zval_dtor(z_tab);
-		efree(z_tab);
+        }
 	}
 }