add_filter( 'get_avatar' , 'my_custom_avatar' , 1 , 5 );
function my_custom_avatar( $avatar, $id_or_email, $size, $default, $alt ) {
$user = false;
if ( is_numeric( $id_or_email ) ) {
$id = (int) $id_or_email;
$user = get_user_by( 'id' , $id );
} elseif ( is_object( $id_or_email ) ) {
if ( ! empty( $id_or_email->user_id ) ) {
$id = (int) $id_or_email->user_id;
$user = get_user_by( 'id' , $id );
}
} else {
$user = get_user_by( 'email', $id_or_email );
}
if ( $user && is_object( $user ) ) {
if ( $user->data->ID == '1' ) {
$avatar="YOUR_NEW_IMAGE_URL";
$avatar = "<img alt="{$alt}" src="https://wordpress.stackexchange.com/questions/180631/{$avatar}" class="avatar avatar-{$size} photo" height="{$size}" width="{$size}" />";
}
}
return $avatar;
}
enter the new image url and paste this code in functions.php
Explaination can be found here.
how to modify avatar