explode用字符串分割，split用正则分割，explode快多了
php文档还说preg_split比split快，所以永远不要用split
Even though I have been a PHP programmer for 4 years or so now, I still discover new things every day. While looking at different ways to split strings based on regular expressions I learned an important lesson.
explode() isn’t the same as split()!
Since I learned Perl before PHP, I prefer using split() and join() instead of explode() andimplode(), respectively. To my surprise, split() is not an alias of explode() while join() is an alias of implode().
The biggest difference is explode() takes a delimiter to split by, while split() takes a regular expression. This means that explode() is going to execute faster. Also, the PHP documentation says that preg_split() is faster than split(), so really there isn’t much of a reason to use split() at all.
