表单提交未被isset检测到

I am trying to detect a form click using if(isset($_POST['appSelecter'])){ however it seems to not be returning true. This might be to do with the fact that my button click returns to the same page which would loose the form data i had just populated. Can someone confirm if my assumption is correct and if so - how would i need to change this?

Thanks

tried to only paste a sample piece of code to not confuse matters - seems i have made things worse - here is the full flow

    <?php
   <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<!--META-->
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Client Portal Login</title>

<!--STYLESHEETS-->
<link href="css/style.css" rel="stylesheet" type="text/css" />

<!--SCRIPTS-->
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js"></script>
<!--Slider-in icons-->
<script type="text/javascript">
$(document).ready(function() {
    $(".username").focus(function() {
        $(".user-icon").css("left","-48px");
    });
    $(".username").blur(function() {
        $(".user-icon").css("left","0px");
    });

    $(".password").focus(function() {
        $(".pass-icon").css("left","-48px");
    });
    $(".password").blur(function() {
        $(".pass-icon").css("left","0px");
    });
});
</script>

</head>
<body>

<!--WRAPPER-->
<div id="wrapper">

    <!--SLIDE-IN ICONS-->
    <div class="user-icon"></div>
    <div class="pass-icon"></div>
    <!--END SLIDE-IN ICONS-->

<!--LOGIN FORM-->
<form name="login-form" class="login-form" action="index.php" method="post">

    <!--HEADER-->
    <div class="header">
    <!--TITLE--><h1>Client Portal Login</h1><!--END TITLE-->
    <!--DESCRIPTION--><span>Please login to your client portal</span><!--END DESCRIPTION-->
    </div>
    <!--END HEADER-->

    <!--CONTENT-->
    <div class="content">
    <!--USERNAME--><input name="username" type="text" class="input username" value="Username" onfocus="this.value=''" /><!--END USERNAME-->
    <!--PASSWORD--><input name="password" type="password" class="input password" value="Password" onfocus="this.value=''" /><!--END PASSWORD-->
    </div>
    <!--END CONTENT-->

    <!--FOOTER-->
    <div class="footer">
    <!--LOGIN BUTTON--><input type="submit" name="submit" value="Login" class="button" /><!--END LOGIN BUTTON-->
    <!--REGISTER BUTTON--><input type="submit" name="submit" value="Register" class="register" /><!--END REGISTER BUTTON-->
    </div>
    <!--END FOOTER-->

</form>

<?php

include("application.php");

if(isset($_POST['submit'])){
    $username=$_POST["username"];
    $password=$_POST["password"];
    $userid = logUserIn($username, $password);
    if($userid > 0){
        $applicationsForUser = getAppInformation($userid);
        printUserApplicationSelectionForm($applicationsForUser);

        if(isset($_POST['appSelecter'])) {
            echo "this is a test message";
        }
    }
}


function printUserApplicationSelectionForm($applicationsForUser){
    echo "<br/>";
    echo "<br/>";
    echo "<br/>";
    echo "<br/>";

    foreach ($applicationsForUser as $app) {        
        ?>
        <form action="index.php" method="post">
            <input type="hidden" name="userid" value="<?php echo $app->getUserid(); ?>">  
            <input type="hidden" name="name" value="<?php echo $app->getName(); ?>">  
            <input type="hidden" name="created" value="<?php echo $app->getDateCreated(); ?>">  
            <input type="hidden" name="invoice" value="<?php echo $app->getInvoice(); ?>">  
            <input type="hidden" name="comment" value="<?php echo $app->getComment(); ?>">  
            <input type="submit" name="appSelecter" value="<?php echo $app->getName(); ?>">
        </form>
        <?php


    }
}


function getAppInformation($userid){
    $applicationsForUser = array();
    $conn = new mysqli('localhost:3306', 'root', '', 'clientportal');
    if ($conn->connect_errno > 0) {
        die('Could not connect: ' . mysql_error());
    }else{
        //we have connected to the database
        $sql = "SELECT * FROM application WHERE userid = '$userid'";
        if(!$val = $conn->query($sql)){
            die('There was an error running the query [' . $db->error . ']');
        }else{
            $index = 0;
            while($row = $val->fetch_assoc()){
                $userid = $row['userid'];
                $name = $row['name'];
                $dateCreated = $row['date'];
                $invoice = $row['invoiceid'];
                $comment = $row['commentsid'];              
                $application = new Application($userid, $name, $dateCreated, $invoice, $comment);
                $applicationsForUser[$index] = $application;
                $index++;
            }
        }
    }
    $conn -> close();   
    return $applicationsForUser; 
}

function logUserIn($username, $password) {

    if(!isset($username) && !isset($password)){
        return -1;
    }

    $result = -1;
    //$conn = mysql_connect('localhost', 'web214-admin-ava', 'secondstory');
    $conn = new mysqli('localhost:3306', 'root', '', 'clientportal');
    if ($conn->connect_errno > 0) {
        die('Could not connect: ' . mysql_error());
    }else{
        //we have connected to the database
        $sql = "SELECT * FROM members WHERE username = '$username' AND password = '$password'";
        if(!$val = $conn->query($sql)){
            die('There was an error running the query [' . $db->error . ']');
        }else{
            while($row = $val->fetch_assoc()){
                $result = $row['id'];
                break;
            }
        }
    }
    $conn -> close();
    return $result;
}


?>

<!--END LOGIN FORM-->

</div>
<!--END WRAPPER-->

<!--GRADIENT--><div class="gradient"></div><!--END GRADIENT-->

</body>
</html>

You have used folowing in the form submit:

onClick="location.href='index.php'" // Making a GET request

This is not submitting the form using POST method. Remove this and it'll work.

Update: There is no submit button with name submit so this condion will not work:

if(isset($_POST['submit']))

Make it:

if(isset($_POST['appSelecter']))

You don't need if(isset($_POST['submit'])) instead use;

if(isset($_POST['appSelecter'])) {

    $username=$_POST["username"];
    $password=$_POST["password"];
    $userid = logUserIn($username, $password);

    if($userid > 0){
        $applicationsForUser = getAppInformation($userid);
        printUserApplicationSelectionForm($applicationsForUser);
    }

}

You dont nee this

onClick="location.href='index.php'"

dont do anything , just apply value to button i, i think you have applied already ,

by location.href your request will be send by GET Method in thgis case no form elements sent to the server

if you allow native form submission then all form elements will be sent to server, in case of multiple forms , the only elements sent realted to that submit button form thats it