tp6 find_in_set

In ThinkPHP 6 (TP6), the `find_in_set` function is used to search for a value within a comma-separated list of values. It returns the position of the value if found, otherwise, it returns 0. Here's an example usage:

use think\db\Raw;

// Assuming you have a model named "User" and a field named "skills" containing a comma-separated list of skills
$skill = 'PHP';

// Query for users with the skill 'PHP' in their skills list
$users = User::where(new Raw("FIND_IN_SET('{$skill}', skills)"))->select();

// You can also use it in the query builder
$users = Db::table('user')->where(new Raw("FIND_IN_SET('{$skill}', skills)"))->select();

// Loop through the results
foreach ($users as $user) {
    // Do something with each user
}

Make sure to properly sanitize or bind the value if it comes from user input to prevent SQL injection attacks.