get_mentors.php

<?php
include 'connect.php';

$skills_id = intval($_GET['skill_id']);
$result = $conn->query("SELECT * FROM hr_dev_plan_skills_mentors sm, hr_dev_plan_mentors m, users u WHERE skills_id = $skills_id and u.userid=m.mentor_id and m.id=sm.mentor_id");

$data = [];
while ($row = $result->fetch_assoc()) {
    $data[] = $row;
}

echo json_encode($data);
?>