Fix argument number, add test. Use RETURN_THROWS().

Author: tstarling

ext/libxml/libxml.c

@@ -1079,8 +1079,8 @@ PHP_FUNCTION(libxml_set_external_entity_loader)
 		fci.object = NULL;
 		fci.named_params = NULL;
 		if (zend_fcall_info_init(callback, 0, &fci, &fcc, NULL, &error) != SUCCESS) {
-			zend_argument_type_error(0, "must be a valid callback or NULL, %s", error);
-			RETURN_FALSE;
+			zend_argument_type_error(1, "must be a valid callback or NULL, %s", error);
+			RETURN_THROWS();
 		}
 		LIBXML(entity_loader).fci = fci;
 		LIBXML(entity_loader).fcc = fcc;

ext/libxml/tests/libxml_set_external_entity_loader_error2.phpt

@@ -0,0 +1,14 @@
+--TEST--
+libxml_set_external_entity_loader() with non-callable argument
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+try {
+	libxml_set_external_entity_loader('nonexistent_function');
+} catch (Throwable $e) {
+	echo "Exception: " . $e->getMessage() . "\n";
+}
+?>
+--EXPECT--
+Exception: libxml_set_external_entity_loader(): Argument #1 ($resolver_function) must be a valid callback or NULL, function "nonexistent_function" not found or invalid function name