MODX Snippet. This divides the [[*content]] into two separate text blocks that are divided by a chunk. You need to assign to it after how many characters you want to insert your chunk. I used it for inserting an image within the content. I found this script online.

contentSplitter

<?php
function splitString($string, $amount)
{
    $start = 0;
    $end = $amount;
 
    while ($end < strlen($string)+$amount) //while $end is less than the length of $string + $amount to make sure it gets it all
    {
        $chunk = substr($string, $start, $amount); //assign to variable instead of array
        $chunk = strrev($chunk); // reverse string created
        $new_chunk = preg_split("/[\s]+/", $chunk, 2); // split reversed string into 2 pieces on the first space.  So you are left with an array. Item [0] being the part of the last word and item [1] the remaining string
 
        $page_text = strrev($new_chunk[1]); // reverse the remaining string back so it is readable
 
        $offset = strlen($new_chunk[0]); // count the length of the part of the word left over so we can substract that from the $end.
 
        $strArray[] = $page_text;  // assign to array
 
        $start = $end - $offset;  // subtract that from the end
        $end = $end + $amount;
    }
return $strArray;
}
 
$myContent = $modx->resource->getContent();
 
$return = splitString($myContent, 1500); //$return = the array of 3600 letter strings
 
$num = count($return); // get number of elements in array
 
$output = '';
 
// loop through the $return array and assign each array element to textchunk so we can print each chunk
for($x=0;$x<$num;$x++) {

if ($x==0){
$output.=$return[$x].'</p>';
$output.=$modx->getChunk($tpl);
}else if($x>=1){
$output.='<p>'.$return[$x].'</p>';

}
}
echo $output;