使用找到的函数here, 您可以将其添加到函数中。php

// retrieves the attachment ID from the file URL
function pippin_get_image_id($image_url) {
    global $wpdb;
    $attachment = $wpdb->get_col($wpdb->prepare("SELECT ID FROM $wpdb->posts WHERE guid=\'%s\';", $image_url )); 
    return $attachment[0]; 
}

$img_url = get_bloginfo(\'url\') . \'/bc/wp-content/uploads/placeholder-image.png\';

if ( $img_id = pippin_get_image_id($img_url) ) {
    // Using wp_get_attachment_image should return your alt text added in the WordPress admin.
    echo wp_get_attachment_image( $img_id, \'full\' );
} else {
    // Fallback in case it\'s not found.
    echo \'<img src="\' . $img_url . \'" alt="" />\';
}

这是对Pippin Function. 由于它返回一个post ID，我们可以使用它来获取另一个文本，该文本保存为post Meta：

/**
 * Get image alt text by image URL
 *
 * @param String $image_url
 *
 * @return Bool | String
 */
function image_alt_by_url( $image_url ) {
    global $wpdb;

    if( empty( $image_url ) ) {
        return false;
    }

    $query_arr  = $wpdb->get_col( $wpdb->prepare( "SELECT ID FROM {$wpdb->posts} WHERE guid=\'%s\';", strtolower( $image_url ) ) );
    $image_id   = ( ! empty( $query_arr ) ) ? $query_arr[0] : 0;

    return get_post_meta( $image_id, \'_wp_attachment_image_alt\', true );
}