这是因为如果使用&&，则两个条件都必须为真。如果任何一个条件为假，则整体条件为假。
PHP代码如下-
<!DOCTYPE html>
<html>
<body>
<?php
$firstCondition= "John";
$secondCondition = "David";
if ($firstCondition == "John" && $secondCondition == "David" && ($firstCondition == "Mike" || $firstCondition == "John")) {
echo "The above condition is true";
} else {
echo "The above condition is not true";
}
?>
</body>
</html>输出结果
The above condition is true