how to check data in php

function showwelcome()
{
echo "

";
echo "";
echo "";
echo "";
echo "

";
}
function checkdata()
{
global $error_array;
if($_POST['name']=="")
{
$error_array[]="plz entr something";
}
}
function showerror()
{
global $error_array;
foreach($error_array as $key)
{
echo $key;
}}
function handledata()
{
echo $_POST['name'];
}
$error_array=array();
if(isset($_POST["welcomeseen"]))
{
checkdata();
if(count($error_array)!=0)
{
showerror();
showwelcome();
}
else
{
handledata();
}
}
else
{
showwelcome();
}