Cannot make custom search permalink to work in a fully custom theme. Search string $_GET['s'] is always empty

Question

I am learning to build a fully custom WordPress theme. I have a search form

<form role="search" method="get" class="search-form" action="<?php echo home_url() ?>/">
   <input type="search" placeholder="Search &hellip;" value="" id="s" name="s" required />
   <button type="submit"><i class="fa fa-search"></i></button>
</form>

which renders the following HTML:

<form role="search" method="get" class="search-form" action="http://local.devsite.com/">
   <input type="search" placeholder="Search &hellip;" value="" id="s" name="s" required />
   <button type="submit"><i class="fa fa-search"></i></button>
</form>

In my search.php template, I currently have the following code to check whether everything works as desired:

if( empty( $_GET['s'] ) ) {
    echo 'No search';
    exit;
}

$s = $_GET['s'];
echo $s;

When I run http://local.devsite.com/?s=sedan, I get the value of $_GET['s'] printed on the search page perfectly

However, I want the URL to look like the following: http://local.devsite.com/search/sedan, so I added the following code in my theme's functions.php file.

function yd_change_search_url() {
    if (  is_search() && ! empty( $_GET['s'] ) ) {
        wp_redirect( home_url( "/search/" ) . urlencode( get_query_var( 's' ) ) );
        exit();
    }
}
add_action( 'template_redirect', 'yd_change_search_url' );

After adding the code, I resaved Settings > Permalinks. But when I run http://local.devsite.com/search/sedan, I get No Search message on the search page.

The phrase No Search is printed when an empty $_GET['s'] is encountered according to the following code that I have added in search.php template.

if( empty( $_GET['s'] ) ) {
    echo 'No search';
    exit;
}

$s = $_GET['s'];
echo $s;

What I am doing wrong? I am following this tutorial.

My ultimate goal is to build a URL with multiple query strings, i.e.
http://local.devsite.com/?s=sedan&mfg=2010&model=Mark%20X&cond=used,

which would ultimately transform after rewriting to this
http://local.mydev.com/sedan/2010/mark-x/used

Answer 1

I figured it out. The error was in my code in search.php template file.

My previous code was this:

if( empty( $_GET['s'] ) ) {
    echo 'No search';
    exit;
}

$s = $_GET['s'];
echo $s;

while it should be this:

if( empty( get_query_var( 's' ) ) ) {
    echo 'No search';
    exit;
}

$s = get_query_var( 's' );
echo $s;

Since there is no literal query string in the URL anymore and it has been redirected to a new URL with a different pattern where I won't be able to grab the value using $_GET['s']