How to use onchange with selectedIndex to pass a value in a hidden field?

[sparky-nyc]

All I want to do is to pass the selectedIndex value in a hidden field at the end of my script. I'm assigning the selected value to $selvalue, which I know is receiving the selectedIndex value (which I can see with the alert window), but $selvalue seems to be in a local scope. In other words, if I try printing $selvalue at the end of the script, it shows up as empty!

Also, I would like to use onchange, since there are other fields in the same form whose values are dependent on the first choice (color). In other words, if possible, I don't want to have to post, and then reload the page.

Can someone please tell me what I'm missing? Thanks!

Here's sample code:

<?PHP
// filename: myscript.php

function choosecolor()
{
include "header.php"; //html header stuff
echo "<form name=\"form1\" action=\"myscript.php\" method=\"post\">\n";
echo "<select name=\"selbox\" onchange=\"\$selvalue = this.options[this.selectedIndex].value;alert(\$selvalue);\" >";
echo " <option value=\"red\">Red</option>";
echo " <option value=\"green\">Green</option>";
echo " <option value=\"blue\">Blue</option>";
echo "</select>\n";
echo "<input type=\"hidden\" name=\"colorchoice\" value=\"$selvalue\">\n";
echo "<input type=\"submit\" value=\"next\">\n";
echo "</form>\n";
echo "\$selvalue = $selvalue\n"; // !!! is empty !!!
...
switch($selvalue)
{
case "red":
echo "my favorite color is red\n";
break;
case "green":
echo "my favorite color is green\n";
break;
case "blue":
echo "my favorite color is blue\n";
break;
}
...
include "footer.php"; //html footer stuff
}

... // other functions

// end of file.
?>

[barand]

why don't you just change the name 'selbox' to 'colorchoice' and forget the hidden field?

[barand]

In addition

the php script runs on the server and generated the html page. At the point in time, $selchoice does not exist as the user cannot select anything until the page is displayed on the browser where javacript runs.

[sparky-nyc]

Got it. I've been playing with your suggestion and I got my code working, but now I have 2 related questions:

1. How can I have a selected value that is submitted, even if the user does not change the default selection?
   (see green in the colorbox1 example below)

2. How can I use the selected value passed from form1 to use as the default selected option in form2?
   (see example below)

Thanks for your help!

<?PHP
// filename: myscript.php

function choosecolor1()
// begin choosecolor1()
{
include "header.php"; //html header stuff
echo "<form name=\"form1\" action=\"myscript.php\" method=\"post\">\n";
echo "<select name=\"colorbox1\" onchange=\"\selcolor.value = this.options[this.selectedIndex].value;alert(selcolor.value);\" >";
echo " <option value=\"red\">Red</option>";
echo " <option selected value=\"green\">Green</option>";
echo " <option value=\"blue\">Blue</option>";
echo "</select>\n";
switch($selvalue)
{
case "red":
echo "my favorite color is red\n";
break;
case "green":
echo "my favorite color is green\n";
break;
case "blue":
echo "my favorite color is blue\n";
break;
}
echo "<input type=\"hidden\" name=\"op\" value=\"choosecolor2\">\n";
echo "<input type=\"hidden\" name=\"selcolor\" value=\"\">\n";
echo "<input type=\"submit\" value=\"next\">\n";
echo "</form>\n";
include "footer.php"; //html footer stuff
// end choosecolor1()
}

function choosecolor2()
// begin choosecolor2()
{
include "header.php"; //html header stuff
echo "<form name=\"form2\" action=\"myscript.php\" method=\"post\">\n";
echo "<select name=\"colorbox2\" onchange=\"\selcolor.value = this.options[this.selectedIndex].value;alert(selcolor.value);\" >";
echo " <option value=\"red\">Red</option>";
echo " <option value=\"green\">Green</option>";
echo " <option value=\"blue\">Blue</option>";
echo "</select>\n";
switch($selvalue)
{
case "red":
echo "my new favorite color is red\n";
break;
case "green":
echo "my new favorite color is green\n";
break;
case "blue":
echo "my new favorite color is blue\n";
break;
}
echo "<input type=\"hidden\" name=\"op\" value=\"choosecolor3\">\n";
echo "<input type=\"hidden\" name=\"selcolor\" value=\"\">\n";
echo "<input type=\"submit\" value=\"next\">\n";
echo "</form>\n";
include "footer.php"; //html footer stuff
// end choosecolor2()
}

... // other functions

// end of file.
?>