Update bcmath.scale when calling bcscale()

We should keep the value of bcmath.scale and the internal
bc_precision global synchronized.

Probably more important than the ability to retrieve bcmath.scale
via ini_get(), this also makes sure that the set scale does not
leak into the next request, as it currently does.

Author: nikic

ext/bcmath/bcmath.c

@@ -542,7 +542,11 @@ PHP_FUNCTION(bcscale)
 			RETURN_THROWS();
 		}
 
-		BCG(bc_precision) = (int) new_scale;
+		zend_string *ini_name = zend_string_init("bcmath.scale", sizeof("bcmath.scale") - 1, 0);
+		zend_string *new_scale_str = zend_long_to_str(new_scale);
+		zend_alter_ini_entry(ini_name, new_scale_str, PHP_INI_USER, PHP_INI_STAGE_RUNTIME);
+		zend_string_release(new_scale_str);
+		zend_string_release(ini_name);
 	}
 
 	RETURN_LONG(old_scale);

ext/bcmath/tests/bcscale_variation003.phpt

@@ -6,13 +6,21 @@ bcscale() return value
 bcmath.scale=0
 --FILE--
 <?php
+var_dump((int) ini_get('bcmath.scale'));
 var_dump(bcscale(1));
+var_dump((int) ini_get('bcmath.scale'));
 var_dump(bcscale(4));
+var_dump((int) ini_get('bcmath.scale'));
 var_dump(bcscale());
+var_dump((int) ini_get('bcmath.scale'));
 var_dump(bcscale());
 ?>
 --EXPECT--
 int(0)
+int(0)
+int(1)
 int(1)
 int(4)
 int(4)
+int(4)
+int(4)