4. PHP array and array sorting

I will listen to all her voices,It's okay to whine,It's okay to brag,Even silent,我都会倾听,因为她是我的玫瑰. ——《小王子》

1.什么是数组

数组是一个能在单个变量中存储多个值的特殊变量.

2.创建数组

(1) 数值数组

带有数字 ID 键的数组

//自动分配 ID 键（ID 键总是从 0 开始）：
$cars=array("Volvo","BMW","Toyota");

//人工分配 ID 键：
$cars[0]="Volvo";
$cars[1]="BMW";
$cars[2]="Toyota";

<?php
$cars=array("Volvo","BMW","Toyota");
echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . ".";
?>

获取数组的长度 - count() 函数：

<?php
$cars=array("Volvo","BMW","Toyota");
echo count($cars);
?>

遍历并打印数值数组中的所有值,可以使用for循环：

<?php
$cars=array("Volvo","BMW","Toyota");
$arrlength=count($cars); 
for($x=0;$x<$arrlength;$x++)
{
    
    echo $cars[$x];
    echo "<br>";
}
?>

(2) 关联数组

带有指定的键的数组,每个键关联一个值

$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");

//or:

$age['Peter']="35";
$age['Ben']="37";
$age['Joe']="43";

<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
echo "Peter is " . $age['Peter'] . " years old.";
?>

遍历并打印关联数组中的所有值,可以使用 foreach 循环

<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
foreach($age as $x=>$x_value)
{
    
    echo "Key=" . $x . ", Value=" . $x_value;
    echo "<br>";
}
?>

(3) 多维数组

包含一个或多个数组的数组

3.数组排序

数组中的元素可以按字母或数字顺序进行降序或升序排列

(1) sort()

对数组进行升序排列

<?php
$numbers=array(4,6,2,22,11);
sort($numbers);
?>

(2) rsort()

对数组进行降序排列

<?php
$numbers=array(4,6,2,22,11);
rsort($numbers);
?>

(3) asort()

根据数组的值,对数组进行升序排列

<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
asort($age);
?>

(4) ksort()

根据数组的键,对数组进行升序排列

<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
ksort($age);
?>

(5) arsort()

根据数组的值,对数组进行降序排列

<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
arsort($age);
?>

(6)krsort()

根据数组的键,对数组进行降序排列

<?php
$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
krsort($age);
?>