如果php中的语句尝试冒号和大括号仍然需要帮助

I have a page where I'm trying to get my search box to perform actions. When there's a search I have 3 sites: Google, wiki, and duckduckgo. When I upload page to the server I'm getting syntax errors. I have never done an if statement in PHP before. I looked at tutorials in w3schools and I am still confused. I have tried colons and curly brackets and I am still confused.

Can someone give me a tip in the right direction?

<form action="search.php" method="get">

<?php
$site = substr(filter_input(INPUT_GET, 'site', FILTER_SANITIZE_STRING), 0, 8);
$terms = substr(filter_input(INPUT_GET, 'terms', FILTER_SANITIZE_STRING), 0, 25);

if ($site=="google") header('Location:https://www.google.com/#q=' . $terms); {
}else{
    if ($site=="Wikipedia")header ('Location:https://www.wikipedia.org/#q='  . $terms); {

    } else ($site=="DuckDuckGo")header ('Location:https://duckduckgo.com/#q=' .$terms);
        endif;
    }
}
?>

You have used the if else syntax terribly wrong. Always the task to be done if an statement is correct should come inside parentheses.

Substitute

if ($site=="google") header('Location:https://www.google.com/#q=' . $terms);{
}else{
if ($site=="Wikipedia")header     ('Location:https://www.wikipedia.org/#q='  . $terms);{
} else ($site=="DuckDuckGo")header ('Location:https://duckduckgo.com/#q=' .$terms);
endif;
}

with the following. It is the correct syntax

if ($site=="google"){ 
    header('Location:https://www.google.com/#q=' .      $terms);
}elseif ($site=="Wikipedia"){
    header ('Location:https://www.wikipedia.org/#q='  . $terms);
}elseif ($site=="DuckDuckGo"){
    header ('Location:https://duckduckgo.com/#q=' .$terms);
}else{
    //if $site doesn't match any of the above
}

try like this. if you have one line in below the if. then ignore the curly {} brace

        if ($site=="google")
            header('Location:https://www.google.com/#q=' . $terms); 
        else if ($site=="Wikipedia")
            header ('Location:https://www.wikipedia.org/#q='  . $terms);
        else if($site=="DuckDuckGo")
            header ('Location:https://duckduckgo.com/#q=' .$terms);
        else 
            //if your site == google not work