Shortcode always showing at the top of the wordpress (before post)

Question

I'm new to WP plugin development and found out that my shortcode is showing at the top of the page, but I want to include it anywhere in the post (not at the TOP).

My code:

function getLotoSecond() {
    $html = file_get_contents_curl('URL__ADDRESS');

    // List
    $start = stripos($html, '<ul id="results-2" class="results-items">');
    $end = stripos($html, '</ul>', $offset = $start);
    $length = $end - $start;

    $list = substr($html, $start, $length);
    //--

    // Regex
    preg_match_all('(<label for="LotoPart_C2_([1-6]|Additional)">([0-9]|[1-9][0-9])<\/label>)', $list, $matches);
    $items = $matches[2];
    //--

    // Output
    echo '<ul>';
    for($i = 0; $i < 7; $i++) {
        if($i == 6) {
            echo '<li style="width:30px;height:30px;border-radius:5px;background-color:#F4A024;color:white;font-size:20px;text-align:center;line-height:30px;display:inline-block;margin:0px 5px 5px 0px;">' . $items[$i] . '</li>';
        } else {
            echo '<li style="width:30px;height:30px;border-radius:5px;background-color:#294A70;color:white;font-size:20px;text-align:center;line-height:30px;display:inline-block;margin:0px 5px 5px 0px;">' . $items[$i] . '</li>';
        }
    }
    echo '</ul>';
    //--
}

And then:

function main($atts) {
    if($atts["type"] == "loto-prvy") {
        getLotoFirst();
    } else if($atts["type"] == "loto-druhy") {
        getLotoSecond();
    }
}
    
add_shortcode('tipo', 'main');

What should be the problem here?

Answer 1

Shortcodes should only return the content, they must not print or echo anything. if you have a function that echo/print some data, then you need to use ob_start and ob_get_clean

Here is how you can use ob functions within your shortcode

function main( $atts ) {
    ob_start();
    
    if ( $atts['type'] == 'loto-prvy' ) {
        getLotoFirst();
    } elseif ( $atts['type'] == 'loto-druhy' ) {
        getLotoSecond();
    }

    $content = ob_get_clean(); // store buffered output content.

    return $content; // Return the content.
}
add_shortcode( 'tipo', 'main' );