PHP basic operators, detailed examples of the difference between single quotes and double quotes

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
<?php 
//双引号可以解析变量和转义字符 
$username = "jack"; 
echo "his name is $username!"; 
echo "<br/>"; 
$username = "小东"; 
//如果是英文的感叹号会正常解析变量 
echo "他的名字是$username!";//他的名字是小东! 
echo "<br/>"; 
//如果是中文的感叹号则会解析不出来 
echo "他的名字是$username！";//他的名字是 
echo "<br/>"; 
//转义字符在这里虽然被解析出来了，但是\n是在源代码里换行 
//浏览器显示只是一个字符的位置 
echo "他的名字是$username,\n他今年20岁了";//他的名字是小东, 他今年20岁了 
echo "<br/>"; 
//为了避免出现错误，推荐使用
字符串连接
的方式 
echo "他的名字是".$username.",他今年20岁了";//他的名字是小东,他今年20岁了 
?>

<?php 
//单引号只是输出字符串字面值， 
//不会解析变量和转义字符。 
//也不会进行语法加亮提示 
$username = &#39;anllin&#39;; 
echo &#39;his name is $username,\n his age is 20.&#39;; 
//output 
//his name is $username,\n his age is 20. 
?>

<?php 
//算术操作符 
$a = 5; 
$b = 3; 
echo $a + $b; 
echo &#39;<br/>&#39;; 
echo $a - $b; 
echo &#39;<br/>&#39;; 
echo $a * $b; 
echo &#39;<br/>&#39;; 
echo $a / $b; 
echo &#39;<br/>&#39;; 
echo $a % $b; 
?>

<?php 
//复合赋值操作符 
$a = 5; 
$b = 3; 
echo $a += $b; 
echo &#39;<br/>&#39;; 
echo $a -= $b; 
echo &#39;<br/>&#39;; 
echo $a *= $b; 
echo &#39;<br/>&#39;; 
echo $a /= $b; 
echo &#39;<br/>&#39;; 
echo $a %= $b; 
echo &#39;<br/>&#39;; 
echo $a .= $b; 
?>

8 
5 
15 
5 
2 
23

<?php 
//
递增递减运算符
 
$a = 5; 
echo ++$a; 
echo &#39;<br/>&#39;; 
echo $a++; 
echo &#39;<br/>&#39;; 
echo --$a; 
echo &#39;<br/>&#39;; 
echo $a--; 
?>

6 
6 
6 
6

<?php 
$a = 5; 
$b = 3; 
$c = 5; 
$d = &#39;5&#39;; 
echo $a == $c; 
echo &#39;<br/>&#39;; 
echo $a === $c; 
echo &#39;<br/>&#39;; 
echo $a == $d; 
echo &#39;<br/>&#39;; 
echo $a != $b; 
echo &#39;<br/>&#39;; 
echo $a !== $d; 
echo &#39;<br/>&#39;; 
echo $a != $b; 
echo &#39;<br/>&#39;; 
echo $a > $b; 
echo &#39;<br/>&#39;; 
echo $b < $c; 
echo &#39;<br/>&#39;; 
echo $a >= $c; 
echo &#39;<br/>&#39;; 
echo $a <= $c; 
?>

1 
1 
1 
1 
1 
1 
1 
1 
1 
1

<?php 
$a = false; 
echo ! $a; 
echo &#39;<br/>&#39;; 
$b = 5; 
$c = 3; 
echo $b > 0 && $c > 0; 
echo &#39;<br/>&#39;; 
echo $b > 0 and $c > 0; 
echo &#39;<br/>&#39;; 
echo $b != 0 || $c != 0; 
echo &#39;<br/>&#39;; 
echo $b != 0 or $c != 0; 
echo &#39;<br/>&#39;; 
?>

1 
1 
1 
1 
1

<?php 
$a = 100; 
echo $a > 60 ? &#39;success&#39;:&#39;fail&#39;; 
?>

<?php 
echo @(100/0); 
?>