# Add customer attribute

```php

$installer = $this;

$installer->startSetup();

$setup = new Mage_Eav_Model_Entity_Setup("core_setup");

$entityTypeId     = $setup->getEntityTypeId("customer");
$attributeSetId   = $setup->getDefaultAttributeSetId($entityTypeId);
$attributeGroupId = $setup->getDefaultAttributeGroupId($entityTypeId, $attributeSetId);

$attributeCode  = "telephone"; // attribute code wgat will be created

$installer->addAttribute(
        "customer",
        $attributeCode,
        array(
            "type"     => "varchar",
            "backend"  => "",
            "label"    => "Telephone",
            "input"    => "text",
            "source"   => "",
            "visible"  => true,
            "required" => false,
            "default"  => "",
            "frontend" => "",
            "unique"   => false,
            "note"     => "Customer telephone"
        )
    );

$attribute = Mage::getSingleton("eav/config")->getAttribute("customer", $attributeCode);

$setup->addAttributeToGroup(
            $entityTypeId,
            $attributeSetId,
            $attributeGroupId,
            $attributeCode,
            "100"  // sort_order
        );

$usedInForms = array(
                    "adminhtml_customer",
                    "checkout_register",
                    "customer_account_create",
                    "customer_account_edit",
                    "adminhtml_checkout"
                );

$attribute->setData("used_in_forms", $usedInForms)
          ->setData("is_used_for_customer_segment", true)
          ->setData("is_system", 0)
          ->setData("is_user_defined", 1)
          ->setData("is_visible", 1)
          ->setData("sort_order", 100)
          ;

$attribute->save();

$installer->endSetup();

```