php explode（）与特殊字符无法正常工作

$this->row['contents'] = strip_tags($this->row['contents']);
$this->words = explode(" ", $this->row['contents']);

The code above should create an array with a key => value pair for each word of $this->row['contents']. Under normal circumstances it works just fine, but with a string such as:

This costs U$ 10.40 per liter.

It will separate as

[0] => This
[1] => Costs U$
[2] => 10.40 per
[3] => liter.

Any ideas how to solve this?

maybe this code help you

$this->words = preg_split('/\s+/', $this->row['contents']);