<?php $age = 21; if($age >= 18 && $age <= 25){ echo '符合当兵条件!'; }else{ echo '不符合当兵条件!'; } ?>
符合当兵条件!
<?php $age = 21; if($age < 18 || $age > 25){ echo '不符合当兵条件!'; }else{ echo '符合当兵条件!'; } ?>
<?php $age = 21; if(!($age < 18 || $age > 25)){ echo '符合当兵条件!'; }else{ echo '不符合当兵条件!'; } ?>
<?php $year = 2020; if($year%4==0 && $year%100!=0 || $year%400==0){ echo $year.'年是闰年!'; }else{ echo $year.'不年是闰年!'; } ?>
2020年是闰年!