Online PHP editor | output for JtnoF

<?php $autocollant_total_ht_lot10 = null; $autocollant_total_ht_lot11 = ""; $autocollant_total_ht_custom = "1,000"; $euro = "€"; if (isset($autocollant_total_ht_custom)) { echo 'ht custom'; echo $autocollant_total_ht_custom . " " .$euro . "\r\n"; } //notice this doesnt output anything because it isnt set if (isset($autocollant_total_ht_lot10)) { echo 'lot 10'; echo $autocollant_total_ht_lot10. " " .$euro. "\r\n"; } //notice this does because the string, while empty is something that isnt null if (isset($autocollant_total_ht_lot11)) { echo 'lot 11'; echo $autocollant_total_ht_lot11. " " .$euro. "\r\n"; } //lets set it to null and see what happens $autocollant_total_ht_lot11 = null; if (isset($autocollant_total_ht_lot11)) { echo 'lot 11 AGAIN'; echo $autocollant_total_ht_lot11. " " .$euro. "\r\n"; } //it doesnt get printed!