在PHP中数组分为两类： 数字索引数组和关联数组。
其中数字索引数组和C语言中的数组一样，下标是为0，1，2…
而关联数组下标可能是任意类型，与其它语言中的hash，map等结构相似。
方法1：foreach
<?php
$sports = array(
'football' => 'good',
'swimming' => 'very well',
'running' => 'not good');
foreach ($sports as $key => $value) {
echo $key.": ".$value."<br />";
}
?>
输出结果：
football: good
swimming: very well
running: not good
方法2：each
<?php
$sports = array(
'football' => 'good',
'swimming' => 'very well',
'running' => 'not good');
while (!!$elem = each($sports)) {
echo $elem['key'].": ".$elem['value']."<br />";
}
?>
输出结果：
football: good
swimming: very well
running: not good
方法3：list & each
<?php
$sports = array(
'football' => 'good',
'swimming' => 'very well',
'running' => 'not good');
while (!!list($key, $value) = each($sports)) {
echo $key.": ".$value."<br />";
}
?>
输出结果：
football: good
swimming: very well
running: not good
