is this the correct way to test for a posted variables existence?

is this the correct way to test for a posted variables existence?

References

Reference NO 1

http://stackoverflow.com/questions/15165179/is-this-the-correct-way-to-test-for-a-posted-variables-existence

Reference NO 2

http://stackoverflow.com/questions/858181/how-to-check-a-not-defined-variable-in-javascript

Reference NO 3

http://www.programmersheaven.com/mb/phpstuff/355987/359239/re-check-that-_post-variable-exists/

Reference NO 4

http://php.net/manual/en/function.isset.php

Reference NO 5

http://kunststube.net/isset/

Reference NO 6

http://techtalk.virendrachandak.com/php-isset-vs-empty-vs-is_null/

Reference NO 7

http://www.w3schools.com/php/php_filter.asp

Reference NO 8

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