问如何仅当头像存在时才显示它？

EN

validate_gravatar($email); // returns true or false

    $user_email = get_the_author_meta('user_email');        

    if(validate_gravatar($user_email)) { 
        $author_avatar = get_avatar( get_the_author_meta( 'user_email', $author_id ), '78', '', get_the_author_meta( 'display_name', $author_id ) );
    }

    // Now just echo where ever you want the image, it will show a default image if no gravatar is present.
    if(isset($author_avatar) && !empty($author_avatar)){
        echo '<img src="'.$author_avatar.'" />';
    }

   // In your Functions.php
   function validate_gravatar($email) {
    $hash = md5(strtolower(trim($email)));
    $uri = 'http://www.gravatar.com/avatar/' . $hash . '?d=404';
    $headers = @get_headers($uri);
    if (!preg_match("|200|", $headers[0])) {
        $has_valid_avatar = FALSE;
    } else {
        $has_valid_avatar = TRUE;
    }
    return $has_valid_avatar;
   }

function ns_filter_avatar($avatar, $id_or_email, $size, $default, $alt, $args) 
{
    $headers = @get_headers( $args['url'] );
    if( ! preg_match("|200|", $headers[0] ) ) {
        return;
    }
    return $avatar; 
}
add_filter('get_avatar','ns_filter_avatar', 10, 6);

get_avatar( $user_email, 45, '404' )

/**
*
* Add custom user profile information
*
*/
add_action( 'show_user_profile', 'ns_show_extra_profile_fields' );
add_action( 'edit_user_profile', 'ns_show_extra_profile_fields' );
function ns_show_extra_profile_fields( $user ) { ?>
  <h3>Extra profile information</h3>
   <table class="form-table">
    <tr>
        <th><label for="image">Profile Image</label></th>
        <td>
            <img src="<?php echo esc_attr( get_the_author_meta( 'image', $user->ID ) ); ?>" style="height:50px;">
            <input type="text" name="image" id="image" value="<?php echo esc_attr( get_the_author_meta( 'image', $user->ID ) ); ?>" class="regular-text" /><input type='button' class="button-primary" value="Upload Image" id="uploadimage"/><br />
            <span class="description">Please upload your image for your profile.</span>
        </td>
    </tr>
   </table>
  <?php
 }

 /**
 * Enqueue a script in the WordPress admin user-edit.php.
 *
 * @param int $pagenow Hook suffix for the current admin page.
 */
 function ns_selectively_enqueue_admin_script( $hook ) {
   global $pagenow;
   if ($pagenow != 'user-edit.php') {
     return;
   }
   wp_enqueue_script('media-upload');
   wp_enqueue_script('thickbox');
   wp_enqueue_style('thickbox');
   wp_register_script( 'profile-image', get_template_directory_uri().'/js/profile-image.js', array('jquery-core'), false, true );
   wp_enqueue_script( 'profile-image' );
  }
  add_action( 'admin_enqueue_scripts', 'ns_selectively_enqueue_admin_script' );

  /*
  * Save custom user profile data
  *
  */
  add_action( 'personal_options_update', 'ns_save_extra_profile_fields' );
  add_action( 'edit_user_profile_update', 'ns_save_extra_profile_fields' );
  function ns_save_extra_profile_fields( $user_id ) {

    if ( !current_user_can( 'edit_user', $user_id ) )
      return false;

    if(isset($_POST['image'])) {
     $imageprofile = sanitize_text_field( wp_unslash( $_POST['image'] ) );
     update_user_meta( $user_id, 'image', $imageprofile );
    }
  }

jQuery(document).ready(function() {
jQuery(document).find("input[id^='uploadimage']").live('click', function(){
    //var num = this.id.split('-')[1];
    formfield = jQuery('#image').attr('name');
    tb_show('', 'media-upload.php?type=image&TB_iframe=true');

    window.send_to_editor = function(html) {
        imgurl = jQuery('img',html).attr('src');
        jQuery('#image').val(imgurl);

        tb_remove();
    }
    return false;
  });
});