PHP and JS "Get" problem

Hello here is my code:

<script type="text/javascript">
function changePage()
{
    selectedValue = document.forms['f1'].s1.value;
    newLocation = "http://127.0.0.1:8080/PolPlan/branze.php?page="+selectedValue;
    window.locatoion = newLocation;
}
</script>

<form name="f1">
   <select name="s1" onChange="javascript:changePage()">
      <option value="1">strona 1</option>
      <option value="2">开发者_如何学JAVAstrona 2</option>
   </select>
</form>

<?php

$selectedValue = $_GET['s1']; 
echo $selectedValue;

?>

I get error on line: "$selectedValue = $_GET['s1'];" Error message: Notice: Undefined index: s1 Please help me with it.

Try using isset:

if (isset($_GET['s1'])) {
$selectedValue = $_GET['s1'];
echo $selectedValue;
}

Also be sure that the variable in your GET is the same as "s1". It looks like it should be "page".

if (isset($_GET['page'])) {
$selectedValue = $_GET['page'];
echo $selectedValue;
}

PHP is saying that the index 's1' of the array $_GET doesn`t exists. Try this:

<script type="text/javascript">
function changePage()
{
    document.forms[0].submit(); // Crossbrowser instruction
}
</script>

<form name="s1" action="http://127.0.0.1/PolPlan/branze.php">
   <select name="s1" onChange="javascript:changePage()">
      <option value="1">strona 1</option>
      <option value="2">strona 2</option>
   </select>
</form>

<?php

$selectedValue = isset($_GET['s1']) ? $_GET['s1'] : ''; 
echo $selectedValue;

?>

Change

$selectedValue = $_GET['s1']; 

to

$selectedValue = $_GET['page']; 

if you want to use s1 you need to submit the form

<form name="f1" action="/PolPlan/branze.php" method="get">
<select name="s1" onChange="document.forms['f1'].submit()">

<script type="text/javascript">
function changePage()
{
    selectedValue = document.forms['f1'].s1.value;
    newLocation = "http://127.0.0.1:8080/PolPlan/branze.php?page="+selectedValue;
    window.locatoion = newLocation;
}
</script>

<form name="f1">
   <select name="s1" onChange="javascript:changePage()">
      <option value="1">strona 1</option>
      <option value="2">strona 2</option>
   </select>
</form>

<?php

$selectedValue = $_GET['page']; 
echo $selectedValue;

?>

s1 is undefined because it doesn't exist as an element of $_GET. If you want to know the identifier of that value, it's what's on the left of the = in the URL, not the name of the form element (in this case – this wouldn't necessarily be the case with, say, POST)

you are sending the value as

$_GET['page']

Tyr this:

<script type="text/javascript">
function changePage()
{
    selectedValue = document.forms['f1'].s1.value;
    if (selectedValue == 0) {
        alert("Please select a valid option");
    } else {
        newLocation = "http://127.0.0.1:8080/PolPlan/branze.php?page="+selectedValue;
        window.location = newLocation;
    }
}
</script>

<form name="f1">
   <select name="s1" onChange="javascript:changePage()">
      <option value="0">Select...</option>
      <option value="1">strona 1</option>
      <option value="2">strona 2</option>
   </select>
</form>

<?php
if (isset($_GET['s1'])) {
    $selectedValue = $_GET['s1']; 
    echo $selectedValue;
}
?>

You can remove the php code.

Hope works for you.