Array Validation - php

Question

I'm trying to learn validation and below is where a form for user to enter the 4 fields which I need to validate the user's entry.
1st question: For the variable $a to check if there's content in error array, where should I define it ?
2nd question: for each field(productname/desc/cat/price), should i create a different array to store the error message ?
<?php
$productName = filter_has_var(INPUT_GET, 'pName') ? $_GET['pName']: null;
$desc = filter_has_var(INPUT_GET, 'description') ? $_GET['description']: null;
$cat = filter_has_var(INPUT_GET, 'category') ? $_GET['category']: null;
$pPrice = filter_has_var(INPUT_GET, 'price') ? $_GET['price']: null;
$productName = trim ($productName);
$desc = trim ($desc);
$cat = trim ($cat);
$pPrice = trim ($pPrice);
echo "<h1>Product details</h1>\n";
$nameerror = array();
if (empty($productName))
{
$nameerror[] = "You have not enter a Product";
}
elseif (strlen($productName) >50)
{
$nameerror[] = "Exceed product field length";
}
if (empty($desc))
{
$nameerror[] = "You have not enter description in the Description field";
}
elseif (strlen($desc) >100)
{
$nameerror[] = "Exceed descrption field length";
}
if (empty($cat))
{
$nameerror[] = "You have not enter category in the Category field";
}
if (empty($pPrice))
{
echo"<p>You have not enter price in the Price field</p>\n";
}
elseif (strlen($pPrice) >10)
{
echo"<p>Exceed price field length</p>\n";
}
if (!empty($nameerror))
for ($a=0;$a<count($nameerror);$a++)
{
echo "$nameerror[$a] <br />\n";
}
else
{
echo "<p>Name: $productName</p>\n";
echo "<p>Description: $desc</p>\n";
echo "<p>Category: $cat</p>\n";
echo "<p>Price: $pPrice</p>\n";
}
?>

Answer 1

Your aim is to collect all the errors in the form and tell the user of those.
Everything is correct except that you are using the wrong array name in your loop. It should be:
for ($a=0;$a<count($nameerror);$a++)
{
echo "$nameerror[$a] <br />\n";
}
Answer to your second question is: No - you can store all your error messages in a single array just as you have already done.