摘自http://blog.csdn.net/doggie1024/article/details/5698615
urlencode:返回字符串，此字符串中除了 -_. 之外的所有非字母数字字符都将被替换成百分号（% ）后跟两位十六进制数，空格则编码为加号（+ ） 。
rawurlencode:功能和urlencode基本一样，采用的是RFC1738编码，因此空格会编码为%20 。
eg:
echo 'sales and marketing/Miami';
echo "<br>";
echo rawurlencode('sales and marketing/Miami');
echo "<br>";
echo urlencode('sales and marketing/Miami'); output：
sales and marketing/Miami
sales%20 and%20 marketing%2FMiami (rawurlencode)
sales+ and+ marketing%2FMiami (urlencode)