Code Example Customer Model in Magento 1.9.3.1

Customer.php

<?php

    /**
     * Authenticate customer
     *
     * @param  string $login
     * @param  string $password
     * @throws Mage_Core_Exception
     * @return true
     *
     */
    public function authenticate($login, $password)
    {
        $this->loadByEmail($login);
        if ($this->getConfirmation() && $this->isConfirmationRequired()) {
            throw Mage::exception('Mage_Core', Mage::helper('customer')->__('This account is not confirmed.'),
                self::EXCEPTION_EMAIL_NOT_CONFIRMED
            );
        }
        if (!$this->validatePassword($password)) {
            throw Mage::exception('Mage_Core', Mage::helper('customer')->__('Invalid login or password.'),
                self::EXCEPTION_INVALID_EMAIL_OR_PASSWORD
            );
        }
        Mage::dispatchEvent('customer_customer_authenticated', array(
           'model'    => $this,
           'password' => $password,
        ));
        return true;
    }
    /**
     * Load customer by email
     *
     * @param   string $customerEmail
     * @return  Mage_Customer_Model_Customer
     */
    public function loadByEmail($customerEmail)
    {
        $this->_getResource()->loadByEmail($this, $customerEmail);
        return $this;
    }