Remove duplicate sentences from a paragraph

So what is the best way of removing duplicate phrases from a paragraph?

$paragraph = "A cow jumped over the moon. It mooed with delight. A cow
jumped over the moon. It mooed with delight. A cow jumped over the
moon. It mooed with delight. A cow jumped over the moon. It mooed
with delight. A cow jumped over the moon. Hello world. It mooed with delight. A cow
jumped over the moon. It mooed with delight. A cow jumped over the
moon. It mooed with delight.";



$phrase = "A cow jumped over the moon. It mooed with delight.";


I'd like to end up with:

$paragraph = "A cow jumped over the moon. It mooed with delight. Hello world.";