Slice array in equal parts. For example array(10) into 3 parts => array(4), array(3), array(3)

slice_arrays.php

<?php

function slice_equal($source, $columns) {
  
  $count      = count($source);
  $perColumn  = floor($count / $columns);
  $overflow   = $count % $columns;
  
  // set start values
  $sliceOffset    = 0;
  $sliceOverflow  = ($overflow > 0) ? 1 : 0;
  $sliceLength    = $perColumn + $sliceOverflow;
  $overflow--;
  
  // slice up the source array
  $return = [];
  while (count($return) < $columns) {
    $return[] = array_slice($source, $sliceOffset, $sliceLength);
    
    // prepare for next slice
    $sliceOffset    += $sliceLength;
    $sliceOverflow  = ($overflow > 0) ? 1 : 0;
    $sliceLength    = $perColumn + $sliceOverflow;
    $overflow--;
  }
  
  // return slices
  return $return;
}

// example
$exampleSource = ['Belize', 'Canada', 'Cuba', 'Dominican Republic', 'El Salvador', 'Guatemala', 'Haiti', 'Honduras', 'Jamaica', 'Puerto Rico', 'USA'];
$slicedArray = slice_equal($exampleSource, 3);

print_r($slicedArray);