如果希望在不使用函数文件的情况下实现此功能，可以使用我提出的简化版本。这是测试代码100%工作

<form id="file_upload" method="post" action="#" enctype="multipart/form-data">
     <input type="file" name="my_file_upload[]" multiple="multiple">
     <input name="my_file_upload" type="submit" value="Upload" />
</form>

<?php if ($_SERVER[\'REQUEST_METHOD\'] == \'POST\') {
    require_once( ABSPATH . \'wp-admin/includes/image.php\' );
    require_once( ABSPATH . \'wp-admin/includes/file.php\' );
    require_once( ABSPATH . \'wp-admin/includes/media.php\' );

    $files = $_FILES["my_file_upload"];
    foreach ($files[\'name\'] as $key => $value) {
        if ($files[\'name\'][$key]) {
            $file = array(
                \'name\' => $files[\'name\'][$key],
                \'type\' => $files[\'type\'][$key],
                \'tmp_name\' => $files[\'tmp_name\'][$key],
                \'error\' => $files[\'error\'][$key],
                \'size\' => $files[\'size\'][$key]
            );
            $_FILES = array("upload_file" => $file);
            $attachment_id = media_handle_upload("upload_file", 0);

            if (is_wp_error($attachment_id)) {
                // There was an error uploading the image.
                echo "Error adding file";
            } else {
                // The image was uploaded successfully!
                echo "File added successfully with ID: " . $attachment_id . "<br>";
                echo wp_get_attachment_image($attachment_id, array(800, 600)) . "<br>"; //Display the uploaded image with a size you wish. In this case it is 800x600
            }
        }
    }
} ?>

感谢@shady-m-rasmyI使用了您提到的代码，第二个foreach循环（在自定义模板部分的下面）似乎没有必要，因为它只执行一次。

foreach ($_FILES as $file => $array) {              
   $newupload = my_handle_attachment($file,$pid);
} 

$newupload = my_handle_attachment( "my_file_upload", $pid);

同一元密钥的多个条目

$values = [ \'red\', \'yellow\', \'blue\', \'pink\' ];
foreach( $values as $value ) {
    // This method uses `add_post_meta()` instead of `update_post_meta()`
    add_post_meta( $item_id, \'color\', $value );
}

HTML

<input type="file" id="id_termine_attachment" multiple="multiple" name="id_termine_attachment[]" value="" size="25" />

function upload_file($_FILES) {

    if (!empty($_FILES[\'id_termine_attachment\'])) {
        $supported_types = array(
            \'application/pdf\',
            \'application/vnd.openxmlformats-officedocument.wordprocessingml.document\',
            \'application/msword\',
            \'image/gif\',
            \'image/jpeg\',
            \'image/png\',
            \'application/zip\'
         );

        $file_arr = reArrayFiles($_FILES[\'id_termine_attachment\']);
        $file_urls = [];

        foreach ($file_arr as $file) {
            $arr_file_type = wp_check_filetype(basename($file[\'name\']));
            $uploaded_type = $arr_file_type[\'type\'];
            if (in_array($uploaded_type, $supported_types)) {
                $upload = wp_upload_bits($file[\'name\'], null, file_get_contents($file[\'tmp_name\']));
                if (isset($upload[\'error\']) && $upload[\'error\'] != 0) {
                    wp_die(\'There was an error uploading your file. The error is: \' . $upload[\'error\']);
                } else {
                    array_push($file_urls, $upload[\'url\']);

                } // end if/else
            } else {
                wp_die("This filetyp is not available!");
            }
        }
        update_post_meta($post_id, \'id_termine_attachment\', $file_urls);
    }
}



function reArrayFiles(&$file_post) {
    $file_ary = array();
    $file_count = count($file_post[\'name\']);
    $file_keys = array_keys($file_post);

    for ($i=0; $i<$file_count; $i++) {
        foreach ($file_keys as $key) {
            $file_ary[$i][$key] = $file_post[$key][$i];
        }
    }

    return $file_ary;
}