split-postcode-padded.php

<?php

/**
 * Split a postcode
 * @param  string $postcode
 * @return array containing both outer and inner postcodes
 */
function split_postcode($postcode)
{
    // remove spaces to be safe
    $postcode = str_replace(' ', '', $postcode);
    // get last 3 characters + trim them
    $postcodeInner = trim(substr($postcode, -3));
    // get remaining characters + trim them to be safe
    $postcodeOuter = trim(str_replace($postcodeInner, '', $postcode));
    // return the split
    return [
        'outer' => str_pad($postcodeOuter, 4, " "),
        'inner' => str_pad($postcodeInner, 4, " "),
    ];
}

split-postcode.php

<?php

/**
 * Split a postcode
 * @param  string $postcode
 * @return array containing both outer and inner postcodes
 */
function split_postcode($postcode)
{
    // remove spaces to be safe
    $postcode = str_replace(' ', '', $postcode);
    // get last 3 characters + trim them
    $postcodeInner = trim(substr($postcode, -3));
    // get remaining characters + trim them to be safe
    $postcodeOuter = trim(str_replace($postcodeInner, '', $postcode));
    // return the split
    return [
        'outer' => $postcodeOuter,
        'inner' => $postcodeInner,
    ];
}