数据库插入外键表

I need help for my phpcode at inserting part where the table have a foreign key and its not able to insert and showing error. user is a foreign key . isTrue is a tinyint datatype. I am using true so i added 1 for isTrue column.

Here is the error displayed : Cannot add or update a child row: a foreign key constraint fails (project.statements, CONSTRAINT fk_statement_user FOREIGN KEY (user) REFERENCES user (user) ON DELETE NO ACTION ON UPDATE NO ACTION)

include "dbconn.php";

$statement = $_POST['statement'];
$isTrue = $_POST['isTrue'];
$user = $_POST["user"];

//for($statement=0;$statement<=5;$statement++){
  //  $query = "INSERT INTO statements(statement, answer, user) VALUES ('$statement','1','junhao') ";
//}

$query = "INSERT INTO statements (statement, isTrue, user) VALUES ('$statement','1','$user')";

$status = mysqli_query($link, $query) or die(mysqli_error($link));
if($status)
{
    $row["status"] = $status;
    $row["message"] = "Contact record is inserted successfully";
    echo json_encode($row);
}else
{
    $row["status"] = $status;
    $row["message"] = "Create new contact unsuccessful.";
    echo json_encode($row);
}

Picture of ERD