used function

1.strpos   查找某个字符第一次出现的下标
strrpos  查找某个字符最后一次出现的下标
如shadow_li_wen  截取shadow  
$a = 'shadow_li_wen';
substr($a,0,strpos($a,'-'));
截取shadow_li  substr($a,0,strrpos($a,'-'));