从输入字符串中删除所有重复项

I am trying to remove duplicate entries from tags input string before inserting them into a database but something is wrong in my code. Tags are separated by commas in this example.

form.html

<input type="text" name="tags[usage]" value="{$smarty.post.tags.usage|escape}" />

items.class.php

require_once ROOT_PATH.'/modules/tags.class.php';
$tagsClass = new tags();

foreach($_POST['tags'] as $type=>$tags) {
    $arr = explode(',', $tags);
    foreach($arr as $tag) {
        $tag = trim($tag);

                $tag = array_unique($tag); 

        if($tag != '') {
            $tagID = $tagsClass->getTagID($tag);

            $mysql->query("
                INSERT INTO `items_tags` (
                    `item_id`,
                    `tag_id`,
                    `type`
                )
                VALUES (
                    '".intval($itemID)."',
                    '".intval($tagID)."',
                    '".sql_quote($type)."'
                )
            ");
        }
    }
}       

I'd appreciate any help.

You're getting a comma seperated string in _POST variable,into this line

foreach($_POST['tags'] as $type=>$tags) 

Try below code

$new_array = explode(",", $_POST['tags']);
$new_array = array_unique($new_array);
foreach ($new_array as $value){
//Your code
}