Array reduce is useful to build strings. For example joining nouns.

Here is the array:

Array ( [0] => cat [1] => dog [2] => fish [3] => hampster [4] => cats [5] => turtles )

First example has a leading 'and' due to empty string initialization.

Animals: and cat and dog and fish and hampster and cats and turtles

Second example tests for first instance and handled as a special case.

Animals: cat and dog and fish and hampster and cats and turtles