Examples of classic operations on PHP arrays (traversing arrays, basic operations)

<?php

索引数组
//数组第一种定义
 $arr = array(1,2,3);
var_dump($arr);
 //数组第二种定义
$arr = [1,2,3];
var_dump($arr);
 //数组第三种定义
$arr[0] = 7;
$arr[1] = "hello";
var_dump($arr);

echo $arr[2];//取值 

关联数组


$arr = array("name"=>"小李","sex"=>"女","age"=>"20");
echo $arr["sex"]; 

遍历数组

//for循环遍历  适用于索引数组
 $arr = [1,5,6,9,4,6,8];
for($i=0;$i<count($arr);$i++){
 echo $arr[$i].&#39;<br>&#39;; 
} ;

//foreach循环遍历  适用于索引和关联数组
$arr = array("name"=>"小李","sex"=>"女","age"=>"20");
foreach($arr as $k=>$v){
 //echo $k.&#39;:&#39;.$v.&#39;<br>&#39;; 
 echo "{$k}:{$v}<br>";
}; 


$arr = [1,5,6,9,4,6,8];
foreach($arr as $k){
 echo $k.&#39;<br>&#39;; 
};


$arr = array("name"=>"小李","sex"=>"女","age"=>"20");
var_dump(each($arr));


 list($a,$b) = array(name,小李);
echo "{$a},{$b}"; 


list和each结合遍历
/* $arr = array("name"=>"小李","sex"=>"女","age"=>"20");
while(list($k,$v)=each($arr)){
 echo "{$k}:{$v}<br>";
} */

指针遍历
/* $arr = array("name"=>"小李","sex"=>"女","age"=>"20");
echo current($arr);//取value
echo key($arr);//取key
next($arr);
echo current($arr);
echo key($arr);
prev($arr);
echo current($arr);
echo key($arr);
end($arr);
echo current($arr);
echo key($arr);
reset($arr);
echo key($arr).&#39;:&#39;.current($arr).&#39;<br>&#39;; */