Magento1 - Remove existing Media Gallery and Add New One at same loop

importimages.php

<?php 
$product = Mage::getModel ( 'catalog/product' );
$product_id = $product->getIdBySku ( $sku);
$product->load ( $product_id );

/**
 * BEGIN REMOVE EXISTING MEDIA GALLERY
 */
$attributes = $product->getTypeInstance ()->getSetAttributes ();
if (isset ( $attributes ['media_gallery'] )) {
    $gallery = $attributes ['media_gallery'];
    //Get the images
    $galleryData = $product->getMediaGallery ();
    foreach ( $galleryData ['images'] as $image ) {
        //If image exists
        if ($gallery->getBackend ()->getImage ( $product, $image ['file'] )) {
            $gallery->getBackend ()->removeImage ( $product, $image ['file'] );
        }
    }
    $product->save ();
}
/**
 * END REMOVE EXISTING MEDIA GALLERY
 */
try {
    $galleryData = explode ( ';', $value );
    foreach ( $galleryData as $gallery_img ) /**
     * @param directory where import image reides
     * @param leave 'null' so that it isn't imported as thumbnail, base, or small
     * @param false = the image is copied, not moved from the import directory to it's new location
     * @param false = not excluded from the front end gallery
     */
    {
        $product->setMediaGallery ( array ('images' => array (), 'values' => array () ) );
        if (file_exists ( Mage::getBaseDir ( 'media' ) . DS . 'import' . $gallery_img )) {
            $product->addImageToMediaGallery ( Mage::getBaseDir ( 'media' ) . DS . 'import' . $gallery_img, array ("thumbnail", "small_image", "image" ), false, false )->save ();
        }
    }
} catch ( Exception $e ) {
    echo $e->getMessage ();
}