dropdown-header.php

<?php
/**
 * Login dropdown in header.
 * @since 2.0
 */
?>

<ul id="login-sign" class="nav navbar-nav navbar-right">
	<li class="dropdown">
		<a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false"><?php _e('Login', 'ab'); ?></a>
		<div class="dropdown-menu">

			<?php 
				/**
				 * Show wordpress social login buttons.
				 */
			?>
			<?php if( do_action( 'wordpress_social_login' ) ): ?>
				<div class="social-login-c clearfix">
					<h4><?php _e('Log in using', 'ab'); ?></h4>
					<?php do_action( 'wordpress_social_login' ); ?>
				</div>
			<?php endif; ?>

			<div class="login-c clearfix">
				<?php 
					$form = wp_login_form(array('echo' => false));
					$form = str_replace('login-username', 'login-username form-group', $form);
					$form = str_replace('login-password', 'login-password form-group', $form);
					$form = str_replace('login-remember', 'login-submit form-group', $form);
					$form = str_replace('button-primary', 'btn btn-success', $form);						
					$form = str_replace('</p>
					<p class="login-submit">', '', $form);
					$form = str_replace('<p', '<div', $form);
					$form = str_replace('</p>', '</div>', $form);
					$form = str_replace('class="input"', 'class="form-control"', $form);
					$form = str_replace('id="user_login"', 'id="user_login" placeholder="'.__('Enter your username', 'ab').'"', $form);
					$form = str_replace('id="user_pass"', 'id="user_pass" placeholder="'.__('Enter your password', 'ab').'"', $form);
					echo $form;	
				?>
				<a href="<?php echo wp_lostpassword_url( ); ?>" class="forget-btn"><?php _e('Rest password', 'ab'); ?></a>
				<a href="<?php echo wp_registration_url(); ?>" class="signup-btn btn btn-primary"><?php _e('New to this site? Register', 'ab'); ?></a>
			</div>
		</div>
	</li>					
</ul>