Splits a string into chunks preferring $min until the end chunk then prefer $max.

str_chunk_min_max.php

<?php
    /**
     * Splits $str into chunks preferring $min until the end chunk. 
     * If the remaining chars will fit in a max chunk then max is used.
     * @param string $str
     * @param integer $min
     * @param integer $max
     */
    public function str_chunk_min_max($str, $min=1, $max=1)
    {
        $strParts = str_split($str, $min);

        if(strlen($str) <= $min) {
            return $strParts;
        }

        $strPartsLastKey = count($strParts) - 1;
        $lastPartSize = strlen(end($strParts));

        /** combine the last strPart to the penultimate strPart if able to fit in the max chunk size */
        if($strPartsLastKey > 1 && $lastPartSize < $max && $lastPartSize !== 0) {

            $currentKey = $strPartsLastKey;
            $maxStr = $strParts[$strPartsLastKey];
            /** remove last value as being appended */
            unset($strParts[$strPartsLastKey]);

            while(strlen($maxStr) < $max) {
                $currentKey--;
                $partChars = str_split($strParts[$currentKey]);    

                while(count($partChars) > 0 && strlen($maxStr) < $max) {
                    $maxStr = array_pop($partChars) . $maxStr;
                }

                if(count($partChars) === 0) {
                    unset($strParts[$currentKey]);
                }
            }
            
            $strParts[] = $maxStr;
        }
        
        return $strParts;
    }