Fix libxml2 2.12.x build issues.
https://github.com/php/php-src/commit/0a39890c967aa57225bb6bdf4821aff7a3a3c082
--- ext/soap/php_sdl.c
+++ ext/soap/php_sdl.c
@@ -332,7 +332,7 @@ static void load_wsdl_ex(zval *this_ptr, char *struri, sdlCtx *ctx, int include)
 	sdl_restore_uri_credentials(ctx);
 
 	if (!wsdl) {
-		xmlErrorPtr xmlErrorPtr = xmlGetLastError();
+		const xmlError *xmlErrorPtr = xmlGetLastError();
 
 		if (xmlErrorPtr) {
 			soap_error2(E_ERROR, "Parsing WSDL: Couldn't load from '%s' : %s", struri, xmlErrorPtr->message);