Fixes #4571: ignore non-string attribute names for AttributeBehavior.

framework/behaviors/AttributeBehavior.php

@@ -93,10 +93,13 @@ class AttributeBehavior extends Behavior
             $attributes = (array) $this->attributes[$event->name];
             $value = $this->getValue($event);
             foreach ($attributes as $attribute) {
+                // ignore attribute names which are not string (e.g. when set by TimestampBehavior::updatedAtAttribute)
+                if (is_string($attribute)) {
                     $this->owner->$attribute = $value;
                 }
             }
         }
+    }
 
     /**
      * Returns the value of the current attributes.

framework/behaviors/BlameableBehavior.php

@@ -54,10 +54,12 @@ class BlameableBehavior extends AttributeBehavior
 {
     /**
      * @var string the attribute that will receive current user ID value
+     * Set this property to be null if you do not want to record the creator ID.
      */
     public $createdByAttribute = 'created_by';
     /**
      * @var string the attribute that will receive current user ID value
+     * Set this property to be null if you do not want to record the updater ID.
      */
     public $updatedByAttribute = 'updated_by';
     /**

framework/behaviors/TimestampBehavior.php

@@ -64,10 +64,12 @@ class TimestampBehavior extends AttributeBehavior
 {
     /**
      * @var string the attribute that will receive timestamp value
+     * Set this property to be null if you do not want to record the creation time.
      */
     public $createdAtAttribute = 'created_at';
     /**
-     * @var string the attribute that will receive timestamp value
+     * @var string the attribute that will receive timestamp value.
+     * Set this property to be null if you do not want to record the update time.
      */
     public $updatedAtAttribute = 'updated_at';
     /**