array_chunk() splits the array into several arrays with size values in them. You may also have an array with less values at the end. You get the arrays as members of a multidimensional array indexed with numbers starting from zero.
By setting the optional preserve_keys parameter to TRUE, you can force PHP to preserve the original keys from the input array. If you specify FALSE new number indicies will be used in each resulting array with indices starting from zero. The default is FALSE.