Even or Odd String Check - php

Question

I'm trying to write a program that checks whether the input string is even or odd and I keep getting errors I can't figure out why.
(i = odd, ii = even, iii = odd, iiii = even) and so on.
I try
<?php
//checking even and odd
echo '<form action="" method="post">';
echo "<input type='text' name='val'>\n";
echo "<button type='submit' name='submit'>Check</button>\n";
echo "</form>";
$val = 0;
if ($_SERVER["REQUEST_METHOD"] == "POST") {
if (empty($_POST["val"])) {
$Err = "<span style ='color: red;'>Required.</span>";
echo $Err;
die();
} else {
$val = $_POST["val"];
}
$even = ($val % 2 == 0);
$odd = ($val % 2 != 0);
if ($val > 0){
if($even){
echo "Sting is even.";
} else {
echo "Sting is odd.";
}
} else {
echo "Error";
}
}
?>

Answer 1

You can't divide a string, you need to check the length. Based on your examples of i, ii, iii, iiii etc:
if(strlen($val) % 2 == 0) {
//even
} else {
//odd
}

Answer 2

Solution
<?php
$val = "10";
if (is_numeric($val)){
if($val % 2 == 0){
echo "Even";
}
else{
echo "Odd";
}
}
else {
echo "Invalid number";
}
?>
Here, is_numeric($val) checks if the input is a valid number and not a string. This will avoid Warning: A non-numeric value encountered
You should further handle the cases where the input is a negative number or a floating-point number.