How to get Magento customer ID

In Magento, you can get the customer ID of a logged-in customer using the following code:

$customer = Mage::getSingleton('customer/session')->getCustomer();
$customerId = $customer->getId();

This code first gets the customer session, and then calls the getCustomer method to get the customer object. The getId method is then called on the customer object to get the customer's ID.

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If you want to get the customer ID by email, you can use the following code

$customer = Mage::getModel('customer/customer')->loadByEmail($email);
$customerId = $customer->getId();

This code loads the customer object by passing the email to the loadByEmail method, and then calls the getId method to get the customer's ID.