diff -urN graphviz-2.34.0/tclpkg/gv/gv_php_init.c graphviz-2.34.0.src/tclpkg/gv/gv_php_init.c
--- graphviz-2.34.0/tclpkg/gv/gv_php_init.c	2013-09-07 03:07:52.000000000 +0200
+++ graphviz-2.34.0.src/tclpkg/gv/gv_php_init.c	2014-01-07 22:51:11.299009504 +0100
@@ -19,11 +19,13 @@
 
 static size_t gv_string_writer (GVJ_t *job, const char *s, size_t len)
 {
+    TSRMLS_FETCH();
     return PHPWRITE(s, len);
 }
 
 static size_t gv_channel_writer (GVJ_t *job, const char *s, size_t len)
 {
+    TSRMLS_FETCH();
     return PHPWRITE(s, len);
 }