--- a/src/http/ngx_http_variables.c
+++ b/src/http/ngx_http_variables.c
@@ -78,6 +78,8 @@ static ngx_int_t ngx_http_variable_nginx
     ngx_http_variable_value_t *v, uintptr_t data);
 static ngx_int_t ngx_http_variable_hostname(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data);
+static ngx_int_t ngx_http_variable_pid(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data);
 
 /*
  * TODO:
@@ -227,6 +229,9 @@ static ngx_http_variable_t  ngx_http_cor
     { ngx_string("hostname"), NULL, ngx_http_variable_hostname,
       0, 0, 0 },
 
+    { ngx_string("pid"), NULL, ngx_http_variable_pid,
+      0, 0, 0 },
+
     { ngx_null_string, NULL, NULL, 0, 0, 0 }
 };
 
@@ -1353,6 +1358,27 @@ ngx_http_variable_hostname(ngx_http_requ
 }
 
 
+static ngx_int_t
+ngx_http_variable_pid(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data)
+{
+    u_char  *p;
+
+    p = ngx_pnalloc(r->pool, NGX_INT64_LEN);
+    if (p == NULL) {
+        return NGX_ERROR;
+    }
+
+    v->len = ngx_sprintf(p, "%P", ngx_pid) - p;
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+    v->data = p;
+
+    return NGX_OK;
+}
+
+
 ngx_int_t
 ngx_http_variables_add_core_vars(ngx_conf_t *cf)
 {