Add 'validate-email.php'

validate-email.php

@@ -0,0 +1,15 @@
+<?php
+
+$mysqli = require __DIR__ . "/database.php";
+
+$sql = sprintf("SELECT * FROM user WHERE email = '%s'", $mysqli->real_escape_string($_GET["email"]));
+                
+$result = $mysqli->query($sql);
+
+$is_available = $result->num_rows === 0;
+
+header("Content-Type: application/json");
+
+echo json_encode(["available" => $is_available]);
+
+?>