Question

PHP如何取二维数组中的某列的最大值和最小值？

Answer 1

需要准备的材料分别是：电脑、php编辑器、浏览器。

1、首先，打开php编辑器，新建php文件，例如：index.php，定义一个二维数组，以取第2列的最值为例。

2、在index.php中，输入代码：

$a = [
[11, 5, 24, 8, 3],
[3, 54, 78, 64, 9],
];
echo 'max=' . max($a[1]) . '<br/>';
echo 'min=' . min($a[1]);

3、浏览器运行index.php页面，此时发现第2列的最大值和最小值都被取出了。

Answer 2

<?
$a = array(
array(3,1,2,5,4),
array(7,8,10,9,6),
array(15,12,14,13,11),
);

$b = $a;
for($i=0; $i<count($b); $i++){
sort($b[$i]);
echo '第'.$i.'列 最小数='.$b[$i][0].' 最大数='.$b[$i][count($b[$i])-1].'<br>';
}
?>

Answer 3

$topic_wrong = array(4) {
[0] => array(4) {
["id"] => string(2) "18"
["topic_id"] => string(3) "219"
["knowpoint_time"] => string(1) "0"
["moexam_time"] => string(1) "0"
}
[1] => array(4) {
["id"] => string(2) "19"
["topic_id"] => string(3) "222"
["knowpoint_time"] => string(1) "0"
["moexam_time"] => string(1) "0"
}
[2] => array(4) {
["id"] => string(2) "20"
["topic_id"] => string(3) "224"
["knowpoint_time"] => string(1) "0"
["moexam_time"] => string(1) "0"
}
[3] => array(4) {
["id"] => string(2) "21"
["topic_id"] => string(3) "225"
["knowpoint_time"] => string(1) "0"
["moexam_time"] => string(1) "0"
}
}
//将数组根据topic_id逆序
array_multisort(array_column($topic_wrong,'topic_id'),SORT_DESC,$topic_wrong);
$max = $topic_wrong[0]['topic_id']

Answer 4

<?
$arr = array(
array(3,1,2,5,4),
array(7,8,10,9,6),
array(15,12,14,13,11),
);
$b = array();
foreach($arr as $key=>$value){
$a=$arr[$key];
$b = array_merge($a,$b);
sort($b);
}
echo $b[0]."<p>".$b[count($b)-1];

Answer 5

<?php
function arrMax($arr,$key,$v=true){
    $s = '';
    foreach($arr as $k){
        $s.= $k[$key].',';
    }
    $s = substr($s,0,-1);
    $v = $v===false?'min':'max';
    eval('$v = '.$v.'('.$s.');');
    return $v;
}//求二维数组最大值或最小值
$arr = array(
        '9'=>array(
                'name'=>'张三',
                'age'=>'30'
            ),
        '6'=>array(
                'name'=>'李四',
                 'age'=>'40'
            ),
        'title'=>array(
                'name'=>'王二',
                 'age'=>'10'
                )
        );
$max = arrMax($arr,'age');
$min = arrMax($arr,'age',false);
var_dump($max);
var_dump($min);
?>