diff --git a/htdocs/user/class/user.class.php b/htdocs/user/class/user.class.php
index 51aefa8d4de..9266ebb4d7f 100644
--- a/htdocs/user/class/user.class.php
+++ b/htdocs/user/class/user.class.php
@@ -751,6 +751,50 @@ class User extends CommonObject
 		}
 	}
 
+	/**
+	 * Sets object to supplied categories.
+	 *
+	 * Deletes object from existing categories not supplied.
+	 * Adds it to non existing supplied categories.
+	 * Existing categories are left untouch.
+	 *
+	 * @param int[]|int $categories Category or categories IDs
+	 */
+	public function setCategories($categories)
+	{
+		// Handle single category
+		if (!is_array($categories)) {
+			$categories = array($categories);
+		}
+
+		// Get current categories
+		require_once DOL_DOCUMENT_ROOT . '/categories/class/categorie.class.php';
+		$c = new Categorie($this->db);
+		$existing = $c->containing($this->id, Categorie::TYPE_USER, 'id');
+
+		// Diff
+		if (is_array($existing)) {
+			$to_del = array_diff($existing, $categories);
+			$to_add = array_diff($categories, $existing);
+		} else {
+			$to_del = array(); // Nothing to delete
+			$to_add = $categories;
+		}
+
+		// Process
+		foreach ($to_del as $del) {
+			if ($c->fetch($del) > 0) {
+				$c->del_type($this, 'user');
+			}
+		}
+		foreach ($to_add as $add) {
+			if ($c->fetch($add) > 0) {
+				$c->add_type($this, 'user');
+			}
+		}
+
+		return;
+	}
 
 	/**
 	 *    	Delete the user