如何在php和mysqli中修复重复的标记名称

Question

I don't know how to explain it, maybe this is understandable. I have 2 table:

1. Table tags: (tagID: '1', '2', '3') (tagName: 'a', 'b', 'b')
2. Table tag_posts: (postID: '1', '1', '2') (tagID: '1', '2', '3')

Output: Post 1 tagged (a[id=1], b[id=2]) and post 2 tagged (b[id=3])

But, i want result like this:

1. Table tags: (tagID: '1', '2') (TagName: 'a', 'b')

2. Table tag_posts: (postID: '1', '1', '2') (tagID: '1', '2', '2')

Output: Post 1 tagged (a[id=1], b[id=2]) and post 2 tagged (b[id=2])

I want on table "tags" tag name, b is 2; not b = 2 and b = 3 (not double tag name)

Php

$last_post_id = mysqli_insert_id($connect);

foreach($tags as $tag){
  $sql = mysqli_query($connect, "SELECT * FROM tb_tags WHERE tagName = '$tag'") or die(mysqli_error());
  $row = mysqli_fetch_array($sql);
  if($row == NULL){
    mysqli_query($connect, "INSERT INTO tb_tags (tagName) VALUES ('$tag')") or die(mysqli_error());
    $last_tag_id = mysqli_insert_id($connect);
    mysqli_query($connect, "INSERT INTO tb_tag_posts (postID, tagID) VALUES ('$last_post_id', '$last_tag_id')") or die(mysqli_error());
  }else{
  // if tags name exists do nothing and take the existing id tag
    mysqli_query($connect, "INSERT INTO tb_tag_posts (postID, tagID) VALUES ('$last_post_id', '".$row['tagID']."')") or die(mysqli_error());
  }
}

Answer 1

mysqli_fetch_array: Returns an array that corresponds to the fetched row or NULL if there are no more rows for the resultset represented by the result parameter. from http://php.net/manual/en/mysqli-result.fetch-array.php

I think that you need to have your code like this: if($row == null){