我有2个变量，如下所示，两个变量的整数长度相同：
$var1 = 2016-08-03
$var2 = 2016-21-23
基本上，我需要将它们比较如下：
Step1: compare 2 from $var1 to 2 from $var2
both are same. proceed
Step2: compare 0 from $var1 to 0 from $var2
both are same. proceed
Step3: compare 1 from $var1 to 1 from $var2
both are same. proceed
Step4: compare 6 from $var1 to 6 from $var2
both are same. proceed
Step5: compare - from $var1 to - from $var2
both are same. proceed
Step6: compare 0 from $var1 to 2 from $var2
Result: $var2 is greater