diff --git a/php/src_base/AccessException.php b/php/src_base/AccessException.php
index 0fe1c6d..13a4d4a 100644
--- a/php/src_base/AccessException.php
+++ b/php/src_base/AccessException.php
@@ -7,7 +7,14 @@ use Exception;
  * Class AccessException: indiquer que la resource ou l'objet auquel on veut
  * accéder n'est pas accessible. il s'agit donc d'une erreur de l'utilisateur
  */
-class AccessException extends Exception {
+class AccessException extends UserException {
+  static final function read_only(?string $dest=null, ?string $prefix=null): self {
+    if ($prefix) $prefix = "$prefix: ";
+    if ($dest === null) $dest = "this property";
+    $message = "$dest is read-only";
+    return new static($prefix.$message);
+  }
+
   static final function immutable_object(?string $dest=null, ?string $prefix=null): self {
     if ($prefix) $prefix = "$prefix: ";
     if ($dest === null) $dest = "this object";
diff --git a/php/src_base/StateException.php b/php/src_base/StateException.php
index 8cc3d05..b54d13a 100644
--- a/php/src_base/StateException.php
+++ b/php/src_base/StateException.php
@@ -1,13 +1,13 @@
 <?php
 namespace nulib;
 
-use Exception;
+use LogicException;
 
 /**
  * Class StateException: indiquer que l'état dans lequel on se trouve est
  * inattendu: il s'agit donc d'un bug
  */
-class StateException extends Exception {
+class StateException extends LogicException {
   static final function not_implemented(?string $method=null, ?string $prefix=null): self {
     if ($method === null) $method = "this method";
     $message = "$method is not implemented";