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PHP分支、循环、php模板语法、html混编技巧
天宁
Original
605 people have browsed it

流程控制:分支

单分支

  1. $age = 15;
  3. if ($age >= 18) {
  4.     echo '恭喜, 已成年,可以观看<br>';
  5. }

双分支

  1. if ($age >= 18) {
  2.     echo '恭喜, 已成年,可以观看<br>';
  3. } else {
  4.     //默认分支
  5.     echo '未成年, 请在家长陪同下观看<br>';
  6. }
  8. //如果分支只有一行代码,可以不写大括号
  9. if ($age >= 18)
  10.     echo '恭喜, 已成年,可以观看<br>';
  11. else
  12.     // 默认分支
  13.     echo '未成年, 请在家长陪同下观看<br>';

多分支

  1. $age = 44;
  2. if ($age >= 18 && $age < 30)
  3.     echo "{$age}岁, 彩礼， 能按揭吗? <br>";
  4. else if ($age >= 30 && $age < 45)
  5.     echo "{$age}岁, 应该成个家了 <br>";
  6. else if ($age >= 45)
  7.     echo "{$age}岁, 房贷快还完了 <br>";
  8. else
  9.     // 未成年， < 18, 默认分支
  10.     echo "{$age}岁, 放学了， 我送你回家 <br>";

多分支语法糖:switch

  1. $age = 15;
  2. switch (true) {
  3.     case $age >= 18 && $age < 30:
  4.         echo "{$age}岁, 彩礼， 能按揭吗? <br>";
  5.         break;
  6.     case $age >= 30 && $age < 45:
  7.         echo "{$age}岁, 应该成个家了 <br>";
  8.         break;
  9.     case $age >= 45:
  10.         echo "{$age}岁, 房贷快还完了 <br>";
  11.         break;
  12.     default:
  13.         echo "{$age}岁, 放学了， 我送你回家 <br>";
  14. }

流程控制:循环

循环本质上还是”分支”

  1. 初始化循环变量,这里用索引当循环变量,$i=0;指向第一个数组元素

    $i = 0;

  2. 循环条件:数组长度 = 最大索引 + 1

    1.  echo count($colors);
    2.  if ($i < count($colors)) {
    3.      echo $colors[$i] . '<br>';
    4.  }

  3. 更新循环条件

    1.  $i = $i + 1;
    2.  if ($i < count($colors)) {
    3.      echo $colors[$i] . '<br>';
    4.  }
    5.  $i = $i + 1;
    6.  if ($i < count($colors)) {
    7.      echo $colors[$i] . '<br>';
    8.  }
    9.  echo '<hr>';

  4. 总结循环三要素

    1. 初始化循环变量: $i =0;
    2. 循环条件: $i < count($colors);
    3. 更新循环条件:$i = $i + 1

while() 来简化以上的分支过程

  1. while(),先判断再循环

    1.  $list  = '<ul style="border:1px solid;background: lightcyan">';
    3.  $i = 0;
    4.  while ($i < count($colors)) {
    5.      $list .= "<li>{$colors[$i]}</li>";
    6.      // 更新条件 
    7.      $i = $i + 1;
    8.  }
    10.  $list .= '</ul>';
    12.  echo $list;

  2. do-while 与上面的区别在于条件判断的时机不同,先循环再判断

    1.  $list  = '<ul style="border:1px solid;background: lightgreen">';
    3.  $i = 0;
    4.  do {
    5.      $list .= "<li>{$colors[$i]}</li>";
    6.      // 更新条件 
    7.      $i = $i + 1;
    8.  } while ($i > count($colors));
    10.  $list .= '</ul>';
    12.  echo $list;

  3. for 可看成 while 的语法糖

    1.  $list  = '<ul style="border:1px solid;background: violet">';
    2.  for ($i = 0; $i < count($colors); $i++) {
    3.      $list .= "<li>{$colors[$i]}</li>";
    4.  }
    5.  $list .= '</ul>';
    6.  echo $list;
    8.  // 中断(break)或跳过某次循环(continue)
    9.  $list  = '<ul style="border:1px solid;background: pink">';
    10.  for ($i = 0; $i < count($colors); $i++) {
    11.      // 只输出前二个
    12.      // if ($i > 1) break;
    13.      // 跳过第2个,只输出第1个和第3个
    14.      if ($i === 1) continue;
    15.      $list .= "<li>{$colors[$i]}</li>";
    16.  }
    17.  $list .= '</ul>';
    18.  echo $list;

数组声明与遍历

数组的声明

  1. $colors = ['red', 'green', 'blue'];
索引数组:键名是从0开始的递增的整数
  1. $colors = [0 => 'red', 1 => 'green', 2 => 'blue'];
  2. printf('<pre>%s</pre>', print_r($colors, true));
关联数组:键名的字符串
  1. $user = ['id' => 5, 'name' => '猪老师', 'score' => 90];
  2. printf('<pre>%s</pre>', print_r($user, true));
  3. echo $user['name'];
二者关系

索引数组实际上关联数组的一个子集,只不过用了数字型的字符串

  1. $colors = ['0' => 'red', '1' => 'green', '2' => 'blue'];
  2. printf('<pre>%s</pre>', print_r($colors, true));
  3. //下面两个都能获取到值green
  4. echo $colors[1], '<br>';
  5. echo $colors['1'], '<br>';

数组遍历

while,for
数组成员还可以是一个数组,多维数组: 二维数组
数据表的查询结果,就是用”二维数组”来表示

foreach (数组 as 键名=>值) {…} , 键名是可选的
  1. $users = [
  2.     0 => ['id' => 5, 'name' => '猪老师', 'gender' => 0, 'age' => 18],
  3.     1 => ['id' => 6, 'name' => '牛老师', 'gender' => 1, 'age' => 30],
  4.     2 => ['id' => 5, 'name' => '狗老师', 'gender' => 0, 'age' => 35],
  5. ];
  7. $table = '<table border="1" width="400" cellspacing="0" cellpadding="3" align="center">';
  8. $table .= '<caption>用户信息表</caption>';
  9. $table .= '<thead bgcolor="#ccc"><tr><th>id</th><th>用户名</th><th>性别</th><th>年龄</th></tr></thead>';
  10. $table .= '<tbody align="center">';
  12. // 遍历这个二维数组
  13. foreach ($users as  $user) {
  14.     // $user 还是一个数组
  15.     print_r($user);
  17.     $table .= '<tr>';
  18.     $table .= '<td>' . $user['id'] . '</td>';
  19.     $table .= '<td>' . $user['name'] . '</td>';
  20.     // 1->true, 0->false 
  21.     $table .= '<td>' . ($user['gender'] ? '女' : '男') . '</td>';
  22.     $table .= '<td>' . $user['age'] . '</td>';
  24.     $table .= '</tr>';
  25. }
  26. $table .= '</tbody></table>';
  28. echo $table;
用二维数组来模拟数据表查询结果集
  1. 代码重要部分,具体代码请看”heredoc,解析内部变量”,只适合少量的操作
    1. // 只查php
    2. if ($stu['course'] === 'php') {
    3.     echo <<< STU <tr>
    4.          <td>{$stu['id']}</td>
    5.          <td>{$stu['name']}</td>
    6.          <td class="active">{$stu['course']}</td>
    7.          <td>{$stu['score']}</td>
    8.          </tr>
    9.     STU;
    10. }
  2. 代码重要部分,具体看”php模板语法”,专门用来写模板
    使用短标签进行简化,一般用于只打印一个变量操作:
    1.  //原本写法
    2.  <td><?php echo $stu['id'] ?></td>
    3.  //简化写法,省略了 php echo
    4.  <td><?= $stu['id'] ?></td>
    PHP模板写法 使用endforeach来表示结尾
    1.  <?php foreach ($stus as $stu) : ?>
    2.      //需要循环操作的代码
    3.  <?php endforeach ?>

heredoc,解析内部变量

  1.     <?php
  2.     // 用二维数组来模拟数据表查询结果集
  3.     $stus = [
  4.         ['id' => 1, 'name' => '刘备', 'course' => 'js', 'score' => 83],
  5.         ['id' => 2, 'name' => '关羽', 'course' => 'php', 'score' => 75],
  6.         ['id' => 3, 'name' => '张飞', 'course' => 'js', 'score' => 52],
  7.         ['id' => 4, 'name' => '孙权', 'course' => 'php', 'score' => 88],
  8.         ['id' => 5, 'name' => '周瑜', 'course' => 'js', 'score' => 65],
  9.         ['id' => 6, 'name' => '孔明', 'course' => 'php', 'score' => 53],
  10.         ['id' => 7, 'name' => '赵云', 'course' => 'js', 'score' => 63],
  11.         ['id' => 8, 'name' => '马超', 'course' => 'js', 'score' => 77],
  12.         ['id' => 9, 'name' => '姜维', 'course' => 'php', 'score' => 93],
  13.         ['id' => 10, 'name' => '黄忠', 'course' => 'js', 'score' => 81],
  14.     ]
  15.     ?>
  17.     <!DOCTYPE html>
  18.     <html lang="zh-CN">
  20.     <head>
  21.         <meta charset="UTF-8">
  22.         <meta http-equiv="X-UA-Compatible" content="IE=edge">
  23.         <meta name="viewport" content="width=device-width, initial-scale=1.0">
  24.         <title>php与html原生混编</title>
  25.         <style>
  26.             table {
  27.                 border-collapse: collapse;
  28.                 width: 360px;
  29.                 text-align: center;
  30.             }
  32.             table th,
  33.             table td {
  34.                 border: 1px solid #000;
  35.                 padding: 5px;
  36.             }
  38.             table caption {
  39.                 font-size: 1.3em;
  40.             }
  42.             table thead {
  43.                 background-color: lightcyan;
  44.             }
  46.             .active {
  47.                 color: red;
  48.             }
  49.         </style>
  50.     </head>
  52.     <body>
  54.         <table>
  55.             <caption>学生成绩表</caption>
  56.             <thead>
  57.                 <tr>
  58.                     <th>ID</th>
  59.                     <th>姓名</th>
  60.                     <th>课程</th>
  61.                     <th>成绩</th>
  62.                 </tr>
  63.             </thead>
  65.             <tbody>
  66.                 <!-- 这里显示的用户数据 -->
  67.                 <?php
  68.                 foreach ($stus as $stu) {
  69.                     // echo "<tr>";
  70.                     // echo "<td>{$stu['id']}</td>";
  71.                     // echo "<td>{$stu['name']}</td>";
  72.                     // echo "<td>{$stu['course']}</td>";
  73.                     // echo "<td>{$stu['score']}</td>";
  74.                     // echo "</tr>";
  76.                     // heredoc, 写模板, 可以解析内部变量
  77.                     // echo <<< STU
  78.                     //     <tr>
  79.                     //         <td>{$stu['id']}</td>
  80.                     //         <td>{$stu['name']}</td>
  81.                     //         <td>{$stu['course']}</td>
  82.                     //         <td>{$stu['score']}</td>
  83.                     //     </tr>
  84.                     // STU;
  86.                     // 只查php
  87.                     if ($stu['course'] === 'php') {
  88.                         echo <<< STU
  89.                         <tr>
  90.                             <td>{$stu['id']}</td>
  91.                             <td>{$stu['name']}</td>
  92.                             <td class="active">{$stu['course']}</td>
  93.                             <td>{$stu['score']}</td>
  94.                         </tr>
  95.                     STU;
  96.                     }
  97.                 }
  98.                 ?>
  99.             </tbody>
  100.         </table>
  102.     </body>
  104.     </html>

php模板语法

  1.     <?php
  2.     // 用二维数组来模拟数据表查询结果集
  3.     $stus = [
  4.         ['id' => 1, 'name' => '刘备', 'course' => 'js', 'score' => 83],
  5.         ['id' => 2, 'name' => '关羽', 'course' => 'php', 'score' => 75],
  6.         ['id' => 3, 'name' => '张飞', 'course' => 'js', 'score' => 52],
  7.         ['id' => 4, 'name' => '孙权', 'course' => 'php', 'score' => 88],
  8.         ['id' => 5, 'name' => '周瑜', 'course' => 'js', 'score' => 65],
  9.         ['id' => 6, 'name' => '孔明', 'course' => 'php', 'score' => 53],
  10.         ['id' => 7, 'name' => '赵云', 'course' => 'js', 'score' => 63],
  11.         ['id' => 8, 'name' => '马超', 'course' => 'js', 'score' => 77],
  12.         ['id' => 9, 'name' => '姜维', 'course' => 'php', 'score' => 93],
  13.         ['id' => 10, 'name' => '黄忠', 'course' => 'js', 'score' => 81],
  14.     ]
  15.     ?>
  17.     <!DOCTYPE html>
  18.     <html lang="zh-CN">
  20.     <head>
  21.         <meta charset="UTF-8">
  22.         <meta http-equiv="X-UA-Compatible" content="IE=edge">
  23.         <meta name="viewport" content="width=device-width, initial-scale=1.0">
  24.         <title>php流程控制的模板语法/替代语法</title>
  25.         <style>
  26.             table {
  27.                 border-collapse: collapse;
  28.                 width: 360px;
  29.                 text-align: center;
  30.             }
  32.             table th,
  33.             table td {
  34.                 border: 1px solid #000;
  35.                 padding: 5px;
  36.             }
  38.             table caption {
  39.                 font-size: 1.3em;
  40.             }
  42.             table thead {
  43.                 background-color: lightcyan;
  44.             }
  46.             .active {
  47.                 color: red;
  48.             }
  49.         </style>
  50.     </head>
  52.     <body>
  54.         <table>
  55.             <caption>学生成绩表</caption>
  56.             <thead>
  57.                 <tr>
  58.                     <th>ID</th>
  59.                     <th>姓名</th>
  60.                     <th>课程</th>
  61.                     <th>成绩</th>
  62.                 </tr>
  63.             </thead>
  65.             <tbody>
  66.                 <!-- php模板语法的目标: html与php代码分离 -->
  67.                 <?php foreach ($stus as $stu) : ?>
  68.                     <!-- "{" => 冒号加php结束标记 -->
  69.                     <!-- 当前已离开了php环境,处于html中  -->
  70.                     <!-- 使用短标签进行简化: 只打印一个变量  -->
  71.                     <!-- <tr>
  72.                         <td><?php echo $stu['id'] ?></td>
  73.                         <td><?php echo $stu['name'] ?></td>
  74.                         <td><?= $stu['course'] ?></td>
  75.                         <td><?= $stu['score'] ?></td>
  76.                     </tr> -->
  78.                     <!-- 只输出成绩大于70分  -->
  79.                     <!-- <?php if ($stu['score'] > 70) : ?>
  80.                         <tr>
  81.                             <td><?php echo $stu['id'] ?></td>
  82.                             <td><?php echo $stu['name'] ?></td>
  83.                             <td><?= $stu['course'] ?></td>
  84.                             <td class="active"><?= $stu['score'] ?></td>
  85.                         </tr>
  86.                     <?php endif ?> -->
  88.                     <!-- 输出全部,并将不及格成绩描红 -->
  89.                     <tr>
  90.                         <td><?php echo $stu['id'] ?></td>
  91.                         <td><?php echo $stu['name'] ?></td>
  92.                         <td><?= $stu['course'] ?></td>
  93.                         <?php $active = $stu['score'] < 60 ? "active" : '' ?>
  94.                         <td class=<?= $active ?>><?= $stu['score'] ?></td>
  95.                     </tr>
  97.                     <!-- 动态设置样式的方法  -->
  99.                 <?php endforeach ?>
  101.             </tbody>
  102.         </table>
  104.     </body>
  106.     </html>
Correcting teacher：PHPzPHPz

Correction status：qualified

Teacher's comments：
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