* 1. foreach($arr as $key => $value) {}
* 2. 原理:将数组$arr按键值对方式依次取出到$key=>$value中,逐个处理,类似于回调
* 3. 如果只对值处理,可以省略$key: foreach($arr as $value) {}
* 4. 特殊适合关联数组,当然也适用于索引数组
$teacher = ['id'=>1001, 'name'=>'peter zhu', 'salary'=> 3000, 'course'=>'php'];
//用for循环来实现关联数组的遍历
for ($i=0; $i<count($teacher); $i++) {echo key($teacher),'=>',current($teacher),'<br>';next($teacher);}echo '<hr color="red">';
//用while循环来实现
reset($teacher);$i = 0;while ($i<count($teacher)) {echo key($teacher),'=>',current($teacher),'<br>';next($teacher);$i++;}echo '<hr color="red">';//foreach($arr as $key=>$value):数组专用的遍历语法结构echo '<h4>讲师信息</h4>';echo '<ul>';foreach ($teacher as $key => $value) { echo '<li>'.$key.':'.$value.'</li>';}echo '</ul>';echo '<hr color="red">';//如果只对值感兴趣echo '<table border="1" cellpadding="3" cellspacing="0" width="300">';echo '<caption>讲师信息表</caption>';echo '<tr bgcolor="lightskyblue"><th>id</th><th>姓名</th><th>工资</th><th>课程</th></tr>';echo '<tr>';foreach ($teacher as $value) { echo '<td align="center">'.$value.'</td>';}echo '</tr>';echo '</table>';echo '<hr color="red">';
//创建一个日期选择器
echo '<p>选择你的生日:</p>';
//生成年
$years = range(1980, 2000);echo '<select name="year">';foreach ($years as $value) { echo '<option>'.$value.'年</option>';}echo '</select>';echo ' ';
//生成月
$months = range(1, 12);echo '<select name="months">';foreach ($months as $value) { echo '<option value='.$value.'>'.sprintf("%02d",$value) .'月</option>';}echo '</select>';echo ' ';
//生成日
$days = range(1, 31);echo '<select name="days">';foreach ($days as $value) { echo '<option value='.$value.'>'.sprintf("%02d",$value) .'日</option>';}echo '</select>';echo ' ';echo '<button>提交</button>';