How to insert my ip into database PHP

I am trying to insert the current time() and $_SERVER['REMOTE_ADDR']; into my database
I have this code

<?php
    require_once("../core/core.php");

    $user_time = time();
    $ip = $_SERVER['REMOTE_ADDR'];
    $sql = "SELECT * FROM userinfo WHERE ip = $ip";
    $result = $conn->query($sql);

    if(!$result) {
        trigger_error('Wrong SQL: ' . $sql . ' Error: ' . $conn->error, E_USER_ERROR); <-- line 10
        echo "Database connection failed.";
    } else {
        if($result->num_rows == 0){
            trigger_error('Wrong SQL: ' . $sql . ' Error: ' . $conn->error, E_USER_ERROR);

            $sql = "INSERT INTO userinfo (ip, time) VALUES ('$ip', '$user_time')";
            $conn->query($sql);
            echo "IP ADDRESS SAVED successfully";
        } else if($result->num_rows >= 1) {
            $sql = "UPDATE userinfo SET time = '$user_time' WHERE `ip` = '$ip'";
            $conn->query($sql);
            echo "IP ADDRESS UPDATED successfully";
        }
    }
?>

But i get an error Fatal error: Wrong SQL: SELECT * FROM userinfo WHERE ip = my_real_ip Error: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '.103.25' at line 1 in /home/appunloc/domain/folder/index.php on line 10