Question

当我使用foreach运行我的变量数组时，我发现当使用加法运算符时，不显示回声字符串。但是回显只有赋值运算符才能显示。使用加法不能回显字符串的原因是什么运营商？

<?php
 $key = 3;
 echo $key+1;echo "<br>";      // 4
 echo "The answer is ".++$key; // The answer is 4
 echo "The answer is ".$key+1; // 1
 //last echo is why can't display string and not getting 4
?>

Answer 1

那是因为你正在用字符串进行数学运算。

"The answer is ".$key+1与

相同

"The answer is 3" + 1 which equals 1;

您需要使用（）来清除范围

$key = 3;
"The answer is ".($key+1) === "The answer is 4"

另外

echo "The answer is ".++$key; // The answer is 4
echo "The answer is ".($key+1); // This would be 5, beause you're incrementing $key by 1 beforehand

使用assign运算符时，不能回显字符串吗？

1 个答案: