PHP variable scope question - php

Question

I'm a beginner to PHP and trying to write a code, that does form validation.
It's nothing fancy just testing it out. I just wrote a function that test the Age input text whether it's a number or not. If it isn't it stores an error in an array and then display that error in another page. I saw this method in a video tutorial , but couldn't do it myself. When i try to invoke that error (not numeric value in Age) it always shows me this error in my add.php page :
Notice: Undefined variable: errors in /home/rafael/www/RofaCorp/add/add.php on line 37
How do i declare a variable that can be accessed through my whole project ?
Here's my code :
form_validation.php
<?php
function validate_number($number) {
global $errors;
if (is_numeric($number)) {
return $number;
}else {
$errors[] = "Value must be number";
}
if (!empty ($errors))
{
header("Location: ../add.php");
exit;
}
}
?>
create_ind.php
<?php require_once '../../include/connection.php'; ?>
<?php require_once '../../include/form_validation.php'; ?>
<?php require_once '../../include/functions_database_infoget.php'; ?>
<?php
$family_id = get_family_info_fam("id");
$ind_name = mysql_real_escape_string($_POST["ind_name"]);
$age = validate_number(mysql_real_escape_string($_POST["age"]));
$gender = $_POST["gender"];
$notes = mysql_real_escape_string($_POST["notes"]);
$add_query = "INSERT INTO individual
( g_id , ind_name , age , gender , notes)
Values ( {$family_id} , '{$ind_name}' , {$age} , '{$gender}' , '{$notes}')";
if(mysql_query($add_query , $connection)){
header("Location: ../../main.php");
exit;
} else {echo "ERROR " . mysql_error() ; }
?>
<?php mysql_close($connection); ?>
add.php (a portion of my code)
<!--Main Content-->
<section id="mainContent">
<header>
<h3>Select where to add new Family/Individual.</h3>
</header>
<article>
<?php
if (count($errors) > 0) {
for($i=0 ; $i < count($errors) ; $i++){
echo "{$errors[$i]}" . "<br/>";
}
}
?>
</article>
</section>

Answer 1

A global variable is only defined while your scripts are processing, as soon as you do header("Location: ../add.php"); you are loading a new page and all variables are lost. That´s what the error message is telling you, there is no variable $errors in add.php.
If you want your error message to persist between different page loads, a session variable is a good option (there are of course others like databases, etc.). Just start the session again in add.php and you have access to the variables stored in the session.

Answer 2

If it is shown in another page, use sessions.
Will allow you to retrieve variables from other pages.
You can use this simple tut http://www.tizag.com/phpT/phpsessions.php