update docs

Author: michalsn

user_guide_src/source/libraries/validation.rst

@@ -858,6 +858,10 @@ Or you can use the following parameters:
 .. literalinclude:: validation/041.php
    :lines: 2-
 
+.. note:: Since v4.8.0, the ``{field}``, ``{param}``, and ``{value}`` placeholders are supported in ``$error``
+    messages and will be replaced with the field's human-readable label (or field name if no label is set),
+    the rule parameter, and the submitted value respectively.
+
 .. _validation-using-callable-rule:
 
 Using Callable Rule
@@ -881,6 +885,10 @@ Or you can use the following parameters:
 .. literalinclude:: validation/047.php
    :lines: 2-
 
+.. note:: Since v4.8.0, the ``{field}``, ``{param}``, and ``{value}`` placeholders are supported in ``$error``
+    messages and will be replaced with the field's human-readable label (or field name if no label is set),
+    the rule parameter, and the submitted value respectively.
+
 .. _validation-available-rules:
 
 ***************

user_guide_src/source/libraries/validation/035.php

@@ -6,6 +6,8 @@ public function even($value, ?string &$error = null): bool
     {
         if ((int) $value % 2 !== 0) {
             $error = lang('myerrors.evenError');
+            // You can also use {field}, {param}, and {value} placeholders:
+            // $error = 'The value of {field} is not even.';
 
             return false;
         }

user_guide_src/source/libraries/validation/041.php

@@ -8,7 +8,7 @@ static function ($value, $data, &$error, $field) {
                 return true;
             }
 
-            $error = 'The value is not even.';
+            $error = 'The value of {field} is not even.';
 
             return false;
         },

user_guide_src/source/libraries/validation/047.php

@@ -13,7 +13,7 @@ public function _ruleEven($value, $data, &$error, $field): bool
             return true;
         }
 
-        $error = 'The value is not even.';
+        $error = 'The value of {field} is not even.';
 
         return false;
     }