Using query as PHP variable in another query - php

Question

I am making a site where you can make posts and read post and now I am writing some code to filter these posts (like sort by 'new' or 'most liked')
I have this as query:
$search_query="SELECT Posts.user, Posts.title, Games.name,
Posts.text, Posts.time, Posts.attachement
FROM Posts
INNER JOIN Games ON Posts.game = Games.id
WHERE Posts.game = '$game'
AND tag = '$tag' AND subtag = '$subtag'"
or die("The search_query on the database has failed!");
The normal $search_query works fine.
Now I want to extend this query if the user wants to sort the posts, for example posts of last week, day etc.:
if(!empty($_POST['time']))
{
$search_query= "SELECT * FROM $search_query
WHERE time < DATE_SUB(now(), INTERVAL $time)";
}
But this query doesn't work, cause I get this error:
mysqli_num_rows() expects parameter 1 to be mysqli_result, bool given in
I have read that this means that there is error in the query.
Does anyone know how I can fix this?

Answer 1

All you need to do is simply add the additional clauses to the existing WHERE
if(!empty($_POST['time']))
{
$search_query .= " AND time < DATE_SUB(now(), INTERVAL $time)";
}
PS the or die() on here makes no sense as you are only putting text into a string variable, not executing it.
$search_query="SELECT Posts.user, Posts.title, Games.name,
Posts.text, Posts.time, Posts.attachement
FROM Posts
INNER JOIN Games ON Posts.game = Games.id
WHERE Posts.game = '$game'
AND tag = '$tag' AND subtag = '$subtag'"
or die("The search_query on the database has failed!");