PHP学习——数组处理函数（一）

<?php
/**
 * Created by phpstorm
 * Author: Aka
 * Date: 2019/12/6
 * Time: 17:06
 **/
//索引数组
$arr1 = array('this','is','first','array','!');
//关联数组
$arr2 = array('firstName'=>'Aka','lastName'=>'Jack','age'=>20,'address'=>"湖南湘潭");
$arr3 = array('iphoneX'=>5000,'mi9'=>4600,'iphone8'=>6000,'honor_v12'=>4396);
$arr4 = array('13'=>5000,26=>'Lx','ip'=>6000,4396=>'clearLove');
//遍历数组
echo '通过for遍历索引数组','<br>';
for($i=0;$i<count($arr1);$i++){
    echo "arr1[$i]=".$arr1[$i],'<br>';
}
echo '通过foreach()遍历关联数组','<br>';
foreach ($arr2 as $key => $value){
    echo $key,'=>',$value,'<br>';
}
var_dump($arr2);
echo '<hr>','以下是数组的排序函数';
echo '用sort()函数进行升序排序','<br>';
sort($arr3);
foreach ($arr3 as $k =>$v){
//    经过sort()之后$arr就会变成一个新的数组，它的key会变成索引,即不保持索引关系
    echo '<br>','key='.$k,'<br>','value='.$v,'<br>';
}
echo '对arr3进行降序排序','<br>';
rsort($arr3);
foreach ($arr3 as $key => $value){
    echo '<br>','key='.$key,'<br>','value='.$value,'<br>';
}
echo '对键名进行升序排列','<br>';
ksort($arr4);
foreach ($arr4 as $key => $value){
    echo '<br>','key='.$key,'<br>','value='.$value,'<br>';
}
echo '对键名进行降序排列','<br>';
krsort($arr4);
foreach ($arr4 as $key => $value){
    echo '<br>','key='.$key,'<br>','value='.$value,'<br>';
}
echo '保持索引关系的同时对值进行升序排列','<br>';
asort($arr4);
foreach ($arr4 as $key => $value){
    echo '<br>','key='.$key,'<br>','value='.$value,'<br>';
}
echo '保持索引关系的同时对值进行降序序排列','<br>';
arsort($arr4);
foreach ($arr4 as $key => $value){
    echo '<br>','key='.$key,'<br>','value='.$value,'<br>';
}