php - 从数组查找key对应的值

Question

php
$arr = [5=>'name',8=>'age',10=>'city'];
$num = '5,10';
$str = '';
//如何查找5,10对应的值，就是输出'name,city',除了foreach还有什么更方便的办法?
foreach($arr as $key=>$value){
    if(strpos($num,$key) !== false) {
        $str.=$value;
    }
}

Answer 1

$arr = array(5=>'name',8=>'age',10=>'city');
$num = '5,10';
var_dump(array_intersect_key($arr,array_flip(explode(',',$num))));

//output
array (size=2)
5 => string 'name' (length=4)
10 => string 'city' (length=4)

Answer 2

<?php

$arr = array(5=>'name',8=>'age',10=>'city');
$num = '5,10';

$str = array();
$explode = explode(',',$num);
foreach($explode as $key){
    if(array_key_exists($key,$arr)){
        array_push($str,$arr[$key]);
    }
}

echo implode(',',$str);

?>

Answer 3

用array_key_exists判断，楼上已给出代码！

Answer 4

除了楼上给出的分解$num后通过array_key_exists在$arr数组寻找相应的值后在implode到一起之外。我给出另外一种通过正则替换的实现方式：

$arr = [5=>'name',8=>'age',10=>'city'];
$num = '5,10';

$res = preg_replace_callback(
    '/(\d+)/', 
    function($matches){
        global $arr;
        return array_key_exists($matches[1], $arr) ? $arr[$matches[1]] : $matches[1];
    },
    $num
);

echo $num."\n";
echo $res;