Collatz Conjecture Solver

gistfile1.php

<?php
if(!isset($_GET['number']) || empty($_GET['number'])) {
	echo '<h3>Please enter a number > 1</h3>';
} elseif(!is_numeric($_GET['number'])) {
	echo '<h3>It has to be a number.</h3>';
}
?>
<form action="" method="get">
<input type="text" name="number">
<input type="submit" value="Go">
</form>
<?php 
if(isset($_GET['number']) && !empty($_GET['number']) && is_numeric($_GET['number'])) {
	echo '<hr>';
	$number = $_GET['number'];
	echo $number.'<br>';
	do {
		if($number % 2 == 0) {
			$number = $number / 2;
		} else {
			$number = $number * 3 + 1;
		}
		echo $number.'<br>';
		
	} while($number > 1);
}
?>