在PHP / MySQL查询中如何以及在何处编写if语句

Question

The following code works well when the correct URL is used like... http://example.com/user.php?id=joe

Where I need help is where do I add an if statement and how should it be written to provide either a default landing page or better, an input field so the visitor can retype the user name and submit it to have the correct page load.

<?php
$pdo = new PDO('mysql:host=localhost;dbname=users', 'root', '');

// retrieve member's data
$ps = $pdo->prepare("SELECT * FROM members WHERE id = ?");
    if(isset($_GET["id"])) {
    $ps->execute(array($_GET["id"]));
    }

$result = $ps->fetch(PDO::FETCH_ASSOC);

extract($result);

echo $First_Name . ' - ' . $Email; 

Any help?

Answer 1

if(!empty($_GET['id'])) {
  // YOUR PREVIOUS CODE HERE
} else {
  // REDIRECT CODE HERE
}

Answer 2

I assume you'd want to wrap all the code with the if statement so it doesn't run unless an id is present.

<?php
    if( isset( $_GET['id'] ) ) {
        //retrieve member data here and render normal page
    }
    else {
        //render landing page
    }
?>

It might be wise to put the code for rendering the two different pages into different functions to help with organization as well.