两个时间相减的函数

<? php function  days( $a , $b ){     $daya = explode ( " . " , $a );     $dayb = explode ( " . " , $b );     $bb = mktime ( 0 , 0 , 0 , $dayb [ 1 ] , $dayb [ 2 ] , $dayb [ 0 ]);     $aa = mktime ( 0 , 0 , 0 , $daya [ 1 ] , $daya [ 2 ] , $daya [ 0 ]);     $day = ( $bb - $aa ) / ( 60 * 60 * 24 );     echo   $day ;} // 例子 days( " 2007.1.10 " , " 2007.1.20 " ); ?>