Automatically split WordPress post content in to 3 columns?

I’m currently using the following code from this tutorial to automatically split the WordPress post content in to 2 columns. However, how would I change this code to output 3 columns instead of only 2?

functions.php code:

function content_split($text, $separator = '<hr/>', $start = false ) {

if ( $start === false) {
$start = strlen($text) / 2;
}

$lastSpace = false;
$split = substr($text, 0, $start - 1);

// if the text is split at a good breaking point already.
if (in_array(substr($text, $start - 1, 1), array(' ', '.', '!', '?'))) {

$split .= substr($text, $start, 1);
// Calculate when we should start the split
$trueStart = strlen($split);

// find a good point to break the text.
} else {

$split = substr($split, 0, $start - strlen($separator));
$lastSpace = strrpos($split, ' ');

if ($lastSpace !== false) {
$split = substr($split, 0, $lastSpace);
}
if (in_array(substr($split, -1, 1), array(','))) {
$split = substr($split, 0, -1);
}

// Calculate when we should start the split
$trueStart = strlen($split);
}
//now we know when to split the text
return substr_replace($text, $separator, $trueStart, 0);

}

index.php code:

<div class="first-column my-column">
<?php $text = get_the_content(); $separator = '</div><div class="second-column my-column">'; echo apply_filters('the_content', content_split($text,$separator)); ?>
</div>