WordPress:: Dynamic Custom Logo To WordPress Theme.

1. You have to enable custom logo feature in theme by using below code in functions.php file

function theme_name_features() {
   /**
    * Add support for core custom logo.
    */
   $logodefault = array(
      'height'      => 75,
      'width'       => 115,
      'flex-height' => true,
      'flex-width'  => true,
      'unlink-homepage-logo' => true,
   );

   add_theme_support('custom-logo', $logodefault);
}

add_action('after_setup_theme', 'theme_name_features');

2. Update Your Logo from the admin panel.

3. Call the updated logo in the header.php using the below code.

<div class="logo">
   <a href="<?php echo site_url() ?>">
      <?php
         $custom_logo_id = get_theme_mod( 'custom_logo' );
         $logo = wp_get_attachment_image_src( $custom_logo_id , 'full' );
         if(has_custom_logo()) {
            echo '<img src="' . esc_url( $logo[0]) . '" alt="' . get_bloginfo( 'name' ) . '">';
         } else {
            echo '<strong>'. get_bloginfo( 'name' ) .'</strong>';
         }
      ?>
   </a>
</div>