Chapter 3 PHP Operators and Control Structure Code_PHP Tutorial

一．字符串插入
双引号与单引号的区别：
1.双引号的使用：

复制代码 代码如下:

//双引号可以解析变量和转义字符
$username = "jack";
echo "his name is $username!";
echo "
";
$username = "小东";
//如果是英文的感叹号会正常解析变量
echo "他的名字是$username!";//他的名字是小东!
echo "
";
//如果是中文的感叹号则会解析不出来
echo "他的名字是$username！";//他的名字是
echo "
";
//转义字符在这里虽然被解析出来了，但是\n是在源代码里换行
//浏览器显示只是一个字符的位置
echo "他的名字是$username,\n他今年20岁了";//他的名字是小东, 他今年20岁了
echo "
";
//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
?>

2.单引号的使用：

复制代码 代码如下:

//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 = 'anllin';
echo 'his name is $username,\n his age is 20.';
//output
//his name is $username,\n his age is 20.
?>

部分常用的转义字符

转义序列	描述
\n	换行符
\r	回车
\t	水平制表图
\\	反斜杠
\$	美元符
\”	双引号

2. Operator

Copy code The code is as follows:

//Arithmetic operator
$a = 5;
$b = 3;
echo $a + $b;
echo '
';
echo $a - $b;
echo '
';
echo $a * $b;
echo '
';
echo $a / $b;
echo '< ;br/>';
echo $a % $b;
?>

8
2
15
1.66666666667
2

Copy code The code is as follows:

//Compound assignment operator
$a = 5;
$b = 3;
echo $a += $b;
echo '
';
echo $a -= $b;
echo '
';
echo $a *= $b;
echo '
';
echo $a /= $b;
echo '< br/>';
echo $a %= $b;
echo '
';
echo $a .= $b;
?>

8
5
15
5
2
23

Copy code The code is as follows:

//increment decrement operator
$a = 5;
echo ++$a;
echo '
';
echo $a++;
echo '
';
echo --$a;
echo '
';
echo $a --;
?>

6
6
6
6

Copy code The code is as follows:

$a = 5;
$b = 3;
$c = 5;
$d = '5' ;
echo $a == $c;
echo '
';
echo $a === $c;
echo '
';
echo $a == $d;
echo '
';
echo $a != $b;
echo '
';
echo $a !== $d;
echo '
';
echo $a != $b;
echo '
';
echo $a > $b;
echo '
';
echo $b < $c;
echo '
';
echo $ a >= $c;
echo '
';
echo $a <= $c;
?>

1
1
1
1
1
1
1
1
1
1

Copy code The code is as follows:

$a = false;
echo ! $a;
echo '
';
$b = 5;
$c = 3;
echo $b > 0 && $c > 0;
echo '
';
echo $b > 0 and $c > 0;
echo '
';
echo $b != 0 || $c != 0;
echo '
echo $b != 0 or $c != 0;
echo '
';
?>

1
1
1
1
1
The operators "and" and "or" have lower precedence than && and ||
Ternary operator

Copy code The code is as follows:

$a = 100;
echo $a > 60 ? 'success' :'fail';
?>

success
Error suppression operator

Copy code The code is as follows :

echo @(100/0);
?>

3. Control structure
If conditional statement

Copy code The code is as follows:

$a = 10;
if ($a > 0)
{
echo 'integer greater than zero';
}
echo '
';
if ($a > 0)
{
echo 'integer greater than zero' ;
}
else if($a < 0)
{
echo 'The integer is less than zero';
}
else
{
echo 'The integer is equal to zero' ';
}
?>

Switch statement

Copy code The code is as follows:

$role = 'admin' ;
switch ($role)
{
case 'admin' :
echo 'admin';
break;
case 'user' :
echo 'normal user ';
break;
case 'guest' :
echo 'guest';
break;
default :
echo 'guest';
break;
}
?>

While loop statement

Copy code The code is as follows:

$a = 10;
while ( $a > 0 )
{
echo $a --;
echo '
';
}
?>

Do while loop statement

Copy code The code is as follows:

$a = 10;
do
{
echo $a --;
echo '
';
}
while ( $a > 0 )
?>

For loop statement

Copy code The code is as follows:

for($a = 0; $a < 10; $a++)
{
echo $a;
echo '< br/>';
}
?>

Break statement

Copy code The code is as follows:

for($ a = 0; $a < 10; $a++)
{
echo $a;
echo '
';
if($a ==5)
{
break; // Terminate the loop, but execute the statement after the loop
}
}
echo 'end of loop';
?>

Exit statement

Copy code The code is as follows:

for($a = 0; $a < 10; $a++)
{
echo $a;
echo '
';
if($a ==5)
{
exit ;//Exit directly, the statements after the loop are not executed
}
}
echo 'end of loop';
?>

Continue statement

Copy code The code is as follows:

for($a = 0; $a < 10; $a++ )
{
echo $a;
echo '
';
if($a ==5)
{
continue;//End this time Loop, continue the next loop, the statements after the loop are still executed
}
}
echo 'end of loop';
?>

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