C API for the Web

void Cos(void) {
    Stack *s;
    char temp[64];

    s = Pop();
    if(!s) {
        Error("Stack error in cos");
        return;
    }
    sprintf(temp,"%f",cos(s->douval));
    Push(temp,DNUMBER);
}
And you could then use it like this:

<html><head><title>Cos Example</title></head>
<body><h1>Cos Example</h1>
<?echo Cos($input)>
</body></html>