Get numbers from string, convert to int and compare to see if is within range of two numbers

Question

I'm trying to get two numbers from a string using substr function and then convert these into a int using $convert = $numbers+0; I then want to see if this number is between two numbers set in an array and return true if it is. Can anyone help me please?

$kacodes = array(27, 28);
$postcodearea = "KA21";
$numbers = substr($postcodearea, 2, 2);
$convert = $numbers +0;

if(($kacodes[0] <= $convert) && ($convert <= $kacodes[1])) {
    return true;
}

Sorry to be vague!

Please see a better picture of what I'm trying to achieve below. I've found out it works if i manually add the string into the function but when adding it into the if / else statement it seems to skip to the else. If that makes sense?

function postcode_form() {
    echo "<form method='post' action=''>
        <input id='postcode' name='postcode' type='text'>
        <input type='submit' name='button'></button>
    </form>";
}

function is_valid_postcode( $postcode = '' )
{   

    $ep = array("AB", "BT", "GY", "HS", "IM", "IV", "JE", "PH", "KW");
    $postcode = strtoupper( $postcode );

    return in_array( $postcode , $ep );

}

function is_valid_postcode_area( $postcodearea )
{   
    $kacodes = array(27, 28);
    $pacodes = array(20, 80);
    $pocodes = array(30, 41);

    $postcodearea = strtoupper( $postcodearea );

    if(substr($postcodearea, 0, 2) === "KA") {

        $numbers = substr($postcodearea, 2, 2);
        $convert = $numbers +0;
        var_dump($convert);

        if( ($kacodes[0] <= $convert) && ($convert <= $kacodes[1]) )  {
            return true;
        }
        else {
            return false;
        }
    }

    else {  
        return false;
    }
}


// define the woocommerce_after_single_product_summary callback 
function action_woocommerce_after_single_product_summary( $evolve_woocommerce_after_single_product_summary, $int ) { 

    postcode_form();

    if( isset( $_POST['postcode'] ) ){

    // Remove unwanted spaces if they're there
    $postcode = trim( $_POST['postcode'] );

    // Extract only the first two characters
    $postcode = substr($postcode, 0, 2 );

    $postcodearea = substr($postcode, 0, 4);

    // Check if the submitted post code is valid
    if( is_valid_postcode( $postcode )){
        echo "Sorry we don't deliver to your postcode";
    }

    elseif(is_valid_postcode_area($postcodearea)) {
        echo "Sorry we don't deliver to your postcode"; 
    }

    else {
        echo "We deliver to your postcode";     
    }



}

}; 

Answer 1

I've managed to work out what was causing the problem. I was using the variable $postcode in $postcodearea which had already been limited to two characters!

Before

 $postcode = trim( $_POST['postcode'] );

    // Extract only the first two characters
    $postcode = substr($postcode, 0, 2 );

    $postcodearea = substr($postcode, 0, 4);

After

        $postcoderaw = trim( $_POST['postcode'] );

        // Extract only the first two characters
        $postcode = substr($postcoderaw, 0, 2 );

        $postcodearea = substr($postcoderaw, 0, 4);