jQuery 'clone' script with other variables doesn't work - php

Question

I have 'cloned' a script, except for the variables the script is exactly the same as the original! But it just doesn't entirely work. it get stuck at:
if(validConnection=="")
{
$('#UsernameConnection').css('border-color','#00ff00');
$('.ErrorUsernameConnection').text('');
checkUsername1 = true;
}
(the rest of the code is below)
I have been checking if I made some mistake in changing the varables but they all seem to match properly. What is wrong? How comes it work fine just with different variables and not this time???
Here is the HTML:
<div id="Connection">
<div class="Connection">
Connection
<strong>×</strong>
</div>
<?php connection(); ?>
<div class="formConnection">
<form method="POST" autocomplete="off" name="Connection">
<label for="Connection">Username:</label><br/>
<input type="text" name="UsernameConnection" id="UsernameConnection"/><br/>
<span class="ErrorUsernameConnection"></span><br/>
<label for="Connection">Password:</label><br/>
<input type="password" name="PasswordConnection" id="PasswordConnection"/>
<span class="ErrorPasswordConnection"></span><br/>
<input type="checkbox" name="checkbox"/><label>Remember me</label><br/>
<input type="submit" name="Connection" value="Log In" id="Connection" class="LogIn"/>
</form>
</div>
Here is the php:
<?php
if(isset($_POST['UsernameConnection']))
{
$Username1 = $_POST['UsernameConnection'];
if(preg_match("/^([a-zA-Z0-9àáâãäåçèéêëìíîïðòóôõöùúûüýÿ]{1,}[._-\s]?)+[a-zA-Z0-9àáâãäåçèéêëìíîïðòóôõöùúûüýÿ]{1,}$/",$Username1))
{
echo "";
}else
{
echo "Invalid";
}
}
?>
and JS:
$(document).ready(function(){
var checkUsername1 = false;
$('#UsernameConnection').keyup(function(){
var Username1 = $('#UsernameConnection').val();
if(Username1=="")
{
$('#UsernameConnection').css('border-color','red');
$('.ErrorUsernameConnection').text('Error message 1');
checkUsername1 = "Username empty";
}else
{
$.post('fonctions/validUsernameConnection.php',{Username1:Username1},function(validConnection)
{
$('.ErrorUsernameConnection').text(validConnection);
if(validConnection=="")
{
$('#UsernameConnection').css('border-color','#00ff00');
$('.ErrorUsernameConnection').text('');
checkUsername1 = true;
}else
{
$('#UsernameConnection').css('border-color','orange');
checkUsername1 = "Username Invalid";
}
});
}
});
});
PS: I'm a little bit lost with all the stack's sites so forgive me if this isn't the right one to post this =/

Answer 1

the problems seems to be with this line
$.post('fonctions/validUsernameConnection.php',{Username1:Username1},
function(validConnection)
In your PHP you should check for $_POST['Username1'] instead of $_POST['UsernameConnection']