第 6 章 PHP 的流程控制功能

作者: 南北东西总相随 | 来源:发表于2017-10-16 21:14 被阅读0次

第 6 章 PHP 的流程控制功能

6.1 转换流程

6.1.1 `if` 语句

<?php
$mood = "happy";
if ($mood == "happy") {
    echo "Hooray! I'm in a good mood!";
}
?>

结果：

Hooray! I'm in a good mood!

6.1.2 使用 `else` 子句的 `if` 语句

<?php
$mood = "sad";
if ($mood == "happy") {
    echo "Hooray! I'm in a good mood!";
} else {
    echo "I'm in a $mood mood.";
}
?>

结果：

I'm in a sad mood.

6.1.3 使用带有 `elseif` 子句的 `if` 语句

<?php
$mood = "sad";
if ($mood == "happy") {
    echo "Hooray! I'm in a good mood!";
} elseif ($mood == "sad") {
    echo "Awww. Don't be down!";
} else {
    echo "I'm neither happy nor sad, but $mood.";
}
?>

结果：

I'm in a sad mood.

6.1.4 `switch` 语句

<?php
$mood = "sad";
switch ($mood) {
    case "happy":
        echo "Hooray! I'm in a good mood!";
        break;
    case "sad":
        echo "Awww. Don't be down!";
        break;
    default:
        echo "I'm neither happy nor sad, but $mood.";
        break;
}
?>

结果：

Awww. Don't be down!

6.1.5 使用 `?` 运算符

<?php
$mood = "sad";
$text = ($mood == "happy") ? "I am in a good mood!" : "I am in a $mood mood.";
echo "$text";
?>

结果：

I am in a sad mood.

6.2 循环

6.2.1 `while` 语句

<?php
$counter = 1;
while ($counter <= 12) {
    echo $counter." times 2 is ".($counter * 2)."<br/>";
    $counter++;
}
?>

结果：

1 times 2 is 2
2 times 2 is 4
3 times 2 is 6
4 times 2 is 8
5 times 2 is 10
6 times 2 is 12
7 times 2 is 14
8 times 2 is 16
9 times 2 is 18
10 times 2 is 20
11 times 2 is 22
12 times 2 is 24

6.2.2 `do...while` 语句

<?php
$num = 395;
do {
    echo "The number is: ".$num."<br/>";
    $num++;
} while ( ($num > 200) && ($num < 400) );
?>

结果：

The number is: 395
The number is: 396
The number is: 397
The number is: 398
The number is: 399

6.2.3 `for` 语句

<?php
for ($counter = 1; $counter <= 12; $counter++) { 
    echo $counter." times 2 is ".($counter * 2)."<br/>";
}
?>

结果：

1 times 2 is 2
2 times 2 is 4
3 times 2 is 6
4 times 2 is 8
5 times 2 is 10
6 times 2 is 12
7 times 2 is 14
8 times 2 is 16
9 times 2 is 18
10 times 2 is 20
11 times 2 is 22
12 times 2 is 24

6.2.4 用 `break` 语句跳出循环

<?php
for ($counter = -4; $counter <= 10; $counter++) { 
    if ($counter == 0) {
        break;
    }
    $temp = 4000/$counter;
    echo "4000 divided by ".$counter." is $temp<br/>";
}
?>

结果：

4000 divided by -4 is -1000
4000 divided by -3 is -1333.33333333
4000 divided by -2 is -2000
4000 divided by -1 is -4000

提示：在 PHP 里用一个数除以零不会导致一个致命的错误。相反，PHP 产生一个警告并继续执行。

<?php
$result = 10/0;
echo "$result";
?>

结果：

<br />
<b>Warning</b>: Division by zero in <b>/Applications/MAMP/htdocs/example.php</b> on line <b>2</b><br />

6.2.5 用 `continue` 语句跳过迭代

程序清单 6.11 使用 continue 语句

<?php
for ($counter = -4; $counter <= 10; $counter++) { 
    if ($counter == 0) {
        continue;
    }
    $temp = 4000/$counter;
    echo "4000 divided by ".$counter." is $temp<br/>";
}
?>

结果：

4000 divided by -4 is -1000
4000 divided by -3 is -1333.33333333
4000 divided by -2 is -2000
4000 divided by -1 is -4000
4000 divided by 1 is 4000
4000 divided by 2 is 2000
4000 divided by 3 is 1333.33333333
4000 divided by 4 is 1000
4000 divided by 5 is 800
4000 divided by 6 is 666.666666667
4000 divided by 7 is 571.428571429
4000 divided by 8 is 500
4000 divided by 9 is 444.444444444
4000 divided by 10 is 400

6.2.6 嵌套循环

<?php
echo "<table style=\"border: 1px solid #000\">\n";
for ($y = 1; $y <= 12; $y++) {
    echo "<tr>\n";
    for ($x = 1; $x <= 12; $x++) {
        echo "<td style=\"border: 1px solid #000; width: 75px; text-align: center;\">";
        echo ($y * $x);
        echo "</td>\n";
    }
    echo "</tr>\n\n";
}
echo "</table>";
?>

结果：

</table>

6.3 代码块和浏览器输出

<?php
$display_prices = true;
if ($display_prices) {
?>
<table border="1">
    <tr>
        <td colspan="3">today's prices in dollars</td>
    </tr>
    <tr>
        <td>$14.00</td>
        <td>$32.00</td>
        <td>$71.00</td>
    </tr>
</table>
<?php
}
?>

结果：

<table border="1">
<tr>
<td colspan="3">today's prices in dollars</td>
</tr>
<tr>
<td>$14.00</td>
<td>$32.00</td>
<td>$71.00</td>
</tr>
</table>

第 6 章 PHP 的流程控制功能

第 6 章 PHP 的流程控制功能

6.1 转换流程

6.1.1 `if` 语句

6.1.2 使用 `else` 子句的 `if` 语句

6.1.3 使用带有 `elseif` 子句的 `if` 语句

6.1.4 `switch` 语句

6.1.5 使用 `?` 运算符

6.2 循环

6.2.1 `while` 语句

6.2.2 `do...while` 语句

6.2.3 `for` 语句

6.2.4 用 `break` 语句跳出循环

6.2.5 用 `continue` 语句跳过迭代

6.2.6 嵌套循环

6.3 代码块和浏览器输出

相关文章

网友评论

延伸阅读

深度阅读

栏目导航

热点阅读

第 6 章 PHP 的流程控制功能

第 6 章 PHP 的流程控制功能

6.1 转换流程

6.1.1 if 语句

6.1.2 使用 else 子句的 if 语句

6.1.3 使用带有 elseif 子句的 if 语句

6.1.4 switch 语句

6.1.5 使用 ? 运算符

6.2 循环

6.2.1 while 语句

6.2.2 do...while 语句

6.2.3 for 语句

6.2.4 用 break 语句跳出循环

6.2.5 用 continue 语句跳过迭代

6.2.6 嵌套循环

6.3 代码块和浏览器输出

相关文章

网友评论

延伸阅读

深度阅读

栏目导航

热点阅读

6.1.1 `if` 语句

6.1.2 使用 `else` 子句的 `if` 语句

6.1.3 使用带有 `elseif` 子句的 `if` 语句

6.1.4 `switch` 语句

6.1.5 使用 `?` 运算符

6.2.1 `while` 语句

6.2.2 `do...while` 语句

6.2.3 `for` 语句

6.2.4 用 `break` 语句跳出循环

6.2.5 用 `continue` 语句跳过迭代