PHP-加减法

我可能有一个非常愚蠢的问题，但我有以下代码：

<?php
$x=2;
$y=4;
print ("iloczyn = ".$x." * ".$y." = ".$x*$y. "<br>");
print ("iloraz = ".$x." / ".$y." = ".$x/$y. "<br>");
print ("suma = ".$x." + ".$y." = ".$x+$y. "<br>");
print ("roznica = ".$x." - ".$y." = ".$x-$y. "<br>");
?>

知道为什么吗？

---

提前谢谢

括号中的“拯救生命”：

$x=2;
$y=4;
print ("iloczyn = ".$x." * ".$y." = ".($x*$y). "<br>");
print ("iloraz = ".$x." / ".$y." = ".($x/$y). "<br>");
print ("suma = ".$x." + ".$y." = ".($x+$y). "<br>");
print ("roznica = ".$x." - ".$y." = ".($x-$y). "<br>");

---

您正在连接，因此它会将它们转换为字符串。把帕伦斯放在周围，它就会工作得很好

$x= 2;
$y= 4;
print ("iloczyn = ".$x." * ".$y." = ".($x*$y). "<br>");
print ("iloraz = ".$x." / ".$y." = ".($x/$y). "<br>");
print ("suma = ".$x." + ".$y." = ".($x+$y). "<br>");
print ("roznica = ".$x." - ".$y." = ".($x-$y). "<br>");

---

运算符优先。当与其他操作一起使用连接时，始终使用括号。非常简单。。。谢谢比我快2分钟！

$x= 2;
$y= 4;
print ("iloczyn = ".$x." * ".$y." = ".($x*$y). "<br>");
print ("iloraz = ".$x." / ".$y." = ".($x/$y). "<br>");
print ("suma = ".$x." + ".$y." = ".($x+$y). "<br>");
print ("roznica = ".$x." - ".$y." = ".($x-$y). "<br>");