调用函数来控制if语句中的确认警报

Question

Good evening .. I have a form where you assign work to a worker, however, if that work is already assigned then user has a choice of either reassigning it or returning to previous page. so I'm trying to write the syntax for a confirm alert that redirects user to one page or another depending on his choice , I placed it within the head section and it goes something like this:

function show_confirm() {
    var con = confirm("Already assigned.. would you like to reassign?");
    if (con ==true) {
       window.location = "reassign.php"
    } else {
       window.location = "index.php"
    }
 }

The question is : how do you call this function depending on an if statement? I have seen some examples on the internet where people place the function (rather than just call it ) directly inside the if statement, but wouldn't that be mixing different kinds of script? So .. how do you call the function from within this if statement? I tried this but it didnt work:

$flat=$_POST['flat'];
$check= mysql_query("SELECT * FROM assignment WHERE flat = '$flat'");
$num= mysql_num_rows($check);
if ($num!=0) {   show_confirm();
 } else { //irrellivant code

Answer 1

Since this is a JavaScript function, you just place the function itself inside the header, and then in PHP, you output the call to the function in your if like this:

if ($num!=0) {
   echo '<script type="text/javascript">show_confirm();</script>';
} else { 
   //irrelevant code
}

PHP is a server-side scripting language, while JavaScript is client-side. You can't call the JavaScript function directly from the server-side like you were trying to do. You can however output javascript to the page via PHP as I have done in my example.