Html-php check box $ _ post is always on

In the following code, echo $ _ POST [& #039; hobbyS & #039;]; returns on. why? How can I get it to return the correct result? {Code...} in the following code, echo $ _ POST ['hobbys ']; the result is on. why? How can I get it to return the correct result?

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In the following code, echo $ _ POST ['hobbys ']; the result is on. why? How can I get it to return the correct result?

When checkbox is selected, the default value is on. after value is set, the value is selected.

Add value = 1 to chexkbox

Http://www.111cn.net/phper/php/37172.htm
Let's take a look at the example here. I have a very detailed explanation!