how to compare data from mysql database with inline if statement to return true or false

This is my code, the first function. fun.php

function post_exists($post_id){
    global $con;
    $post_id = (int)$post_id;
    return (mysqli_fetch_array(mysqli_query($con, "SELECT COUNT(post_id) FROM home_post WHERE  post_id='$post_id'"), MYSQLI_NUM) != 0) ? true : false;
}

This is the function call in index.php

if(post_exists(23) === true){
    echo "<script>alert('working oo')</script>";
}

function usually return true when the argument is false. what i want is, if the argument is true(which means if the data exist in my database)return true if is false return false .