第五章 数组

1.创建数组 array() 、[]、 list() 、 range()

 "bar",
    "bar" => "foo",
);

//2.用[] 创建
// 自 PHP 5.4 起
$array = [
    "foo" => "bar",
    "bar" => "foo",
];

//3.用list()提取数组
$info = array('coffee', 'brown', 'caffeine');
// 列出所有变量
$info = array('coffee', 'brown', 'caffeine');
list($drink, $color, $power) = $info;
echo "$drink is $color and $power makes it special.\n";

//使用预定义的值范围填充数组range()

$die = range(1, 6);
//*类似指定$die = array(1, 2, 3, 4, 5, 6);

$even =range(0, 10, 2);
//$even = array(0, 2, 4, 6, 8, 10);

$letters = range("A", "D");
//$letters = array("A", "B", "C", "D");
?>

2.判断数组 is_array() ;

boolean is_array(mixed variable)

3.输出数组

//1.foreach
$states = array("Ohio", "Florida", "Texas");
foreach ($states as $state) {
    echo "$state
";
}

//打印数组用于测试
print_r($states) 

4.添加和删除数组元素（push pop shift unshift）

//1.在数组头添加元素 array_unshift()

$states = array("Ohio", "New York");
array_unshift($states, "California", "Texas");

//$states = array("California", "Texas", "Ohio", "New York");

//2.在数组尾添加元素 array_push()

$states = array("Ohio", "New York");
array_push($states, "California", "Texas");

//$states = array( "Ohio", "New York", "California", "Texas");

//3.从数组头删除元素 array_shift()

$states = array( "Ohio", "New York", "California", "Texas");
$state = array_shift($states);

//$states = array("New York", "California", "Texas");
//$state = array( "Ohio");

//4.从数组尾删除元素 array_pop()
$states = array( "Ohio", "New York", "California", "Texas");
$state = array_pop($states);

//$states = array("Ohio", "New York", "California");
//$state = array( "Texas");

5.定位数组元素

//1.搜索数组 in_array()
$state = "Ohio";
$states = array("California", "Hawaii", "Ohio", "New York");
if(in_array($state, $states)) echo "not to worry, $state is smoke-free";

//2.搜索关联数组键
$state["Delaware"] = "December 7, 1787";
$state["Pennsylvania"] = "December 12, 1787";
$state["Ohio"] = "March 1, 1803";

if(array_key_exists("Ohio", $state))
    printf("Ohio joined the Union on %s", $state["Ohio"]);

//3.搜索关联数组值 array_search()

$state["Ohio"] = "March 1";
$state["Delaware"] = "December 7";
$state["Pennsylvania"] = "December 12";

$founded = array_search("December 7", $state);

if($founded)
    printf("%s was founded on %s",$founded ,$state[$founded]);

//4.获取数组键 array_keys()

$state["Ohio"] = "March 1";
$state["Delaware"] = "December 7";
$state["Pennsylvania"] = "December 12";

$keys = array_keys($state);
print_r($keys);

//Array ( [0] => Ohio [1] => Delaware [2] => Pennsylvania )

//4.获取数组值 array_values()

$state["Ohio"] = "March 1";
$state["Delaware"] = "December 7";
$state["Pennsylvania"] = "December 12";

$values = array_values($state);
print_r($values);

//Array ( [0] => March 1 [1] => December 7 [2] => December 12 )

//5.遍历数组

//a.获取当前数组键key()
//b.获取当前数组值current()
//c.获取当前数组键和值each()

//6.移动数组指针

//a.将指针移动到下一个数组位置 next()
//b.将指针移动到前一个数组位置 prev()
//c.将指针移动到第一个数组位置 reset()
//d.将指针移动到最后一个数组位置 end()

//7.向函数传递组值 array_walk() 用于表单
function sanitize_data($value, $key) {
    $value = strip_tags($value);
}

array_walk($_POST['keyword'], "sanitize_data");


//8.确定数组的大小和唯一性
//a.确定数组的大小count()
//b.统计数组元素出现的频度array_count_values(array array)
//c.确定唯一的数组元素array_unique()

//9.数组排序

//a.逆置数组元素顺序 array_reverse()
//b.置换数组键和值 array_flip()
//c.数组排序 sort()  各元素按值由低到高的顺序排列
//d.保持键/值对的条件下对数组排序 asort()
//e.以逆序对数组排序rsort()
//f.保持键/值对的条件下以逆序对数组排序arsort()
//g.数组自然排序 natsort()
//h.不区分大小写的自然排序 natcasesort()
//i.按键值对数组排序  ksort()
//j.以逆序对数组键排序 krsort()
//k.根据用户自定义规则排序 usort

//10.合并、拆分、接合和分解数组

//a.合并数组 array_merge()
//b.递归追加数组 array_merge_recursive()
//c.合并两个数组 array_combine
//e.拆分数组 array_slice()
//f.接合数组 array_splice()
//g.求数组的交集array_intersect()
//h.求关联数组的交集 array_intersect_assoc()
//i.求数组的差集 array_diff()
//j.求关联数组的差集 array_diff_assoc()

//11.其他有用的数组函数

//a.返回一组随机的键 array_rand()
//b.随机洗牌数组元素 shuffle()
//c.对数组中的值求和 array_sum()
//e.划分数组 array_chunk()  input_array()