PHP - 如何获取多维数组的特定值

Question

我是 PHP 的初学者，所以基本上我有一个没有指定键的数组，只有数组的值。 我想得到去春假的人的名字（== true）。 我试过这个，但它不起作用......

$liste = [
  ['name' => 'Elsa', 'job' => 'Student', 'springbreak' => 'true' ],
  ['name' => 'Chris', 'job' => 'Teacher', 'springbreak' => 'true' ],
  ['name' => 'Zob', 'job' => 'Student', 'springbreak' => 'false' ],
  ['name' => 'Ken', 'job' => 'Teacher', 'springbreak' => 'true' ],
  ['name' => 'Ryan', 'job' => 'Student', 'springbreak' => 'false' ],
  ['name' => 'Tenta', 'job' => 'Teacher', 'springbreak' => 'true' ]

];

  foreach($liste as $line){
        foreach($line as $value){
          if ($value['springbreak'] == true)
               echo $value['name'];
        }
  }

输出应该是：Elsa,Chris,Ken,Tenta

Answer 1

您可以使用array_filter 、 array_map和join ：

<?php
$liste = [
  ['name' => 'Elsa', 'job' => 'Student', 'springbreak' => 'true'],
  ['name' => 'Chris', 'job' => 'Teacher', 'springbreak' => 'true'],
  ['name' => 'Zob', 'job' => 'Student', 'springbreak' => 'false'],
  ['name' => 'Ken', 'job' => 'Teacher', 'springbreak' => 'true'],
  ['name' => 'Ryan', 'job' => 'Student', 'springbreak' => 'false'],
  ['name' => 'Tenta', 'job' => 'Teacher', 'springbreak' => 'true']
];

// Filter to only keep values with springbreak to true
$springbreak_only = array_filter($liste, function($entry) { return $entry['springbreak'] === 'true'; });

// Grab the names (and ditch the rest)
$springbreak_names = array_map(function($entry) { return $entry['name']; }, $springbreak_only);

// Output the comma-separated names
echo join(', ', $springbreak_names);

在线片段

使用array_reduce替代（只会循环一次）：

$springbreak_names = array_reduce($liste, function($springbreak_names, $entry) {
  if ($entry['springbreak'] === 'true')
    $springbreak_names[] = $entry['name'];
  return $springbreak_names;
}, []);

echo join(', ', $springbreak_names);

请参阅@don't anger me's answer以获得另一个简单的解决方案，功能较少但也更直接。

注意：如果可以，您可能应该使用布尔值true而不是'true' （字符串）。

Answer 2

为什么您现有的代码不起作用？

因为您使用了不必要的两个foreach()而单个foreach()可以解决问题。 另一个原因是你像这样比较$line['springbreak'] == true应该是$line['springbreak'] == 'true'

因此，使用您现有的代码。 咱们试试吧，

foreach($liste as $line){
    if ($line['springbreak'] == 'true')
        echo $line['name'];
}

为什么不简单的foreach()循环和implode()加入 springbreak为true的名称？

<?php
$liste = [
    ['name' => 'Elsa', 'job' => 'Student', 'springbreak' => 'true' ],
    ['name' => 'Chris', 'job' => 'Teacher', 'springbreak' => 'true' ],
    ['name' => 'Zob', 'job' => 'Student', 'springbreak' => 'false' ],
    ['name' => 'Ken', 'job' => 'Teacher', 'springbreak' => 'true' ],
    ['name' => 'Ryan', 'job' => 'Student', 'springbreak' => 'false' ],
    ['name' => 'Tenta', 'job' => 'Teacher', 'springbreak' => 'true' ]
];
$names = [];
foreach($liste as $list){
    if($list['springbreak']=='true'){
        $names[] = $list['name'];
    }
}
echo implode(',',$names);
?>

输出：

Elsa,Chris,Ken,Tenta

演示： https : //3v4l.org/B7Bo6

Answer 3

你忘记了 if 语句。

foreach($liste as $line){
    foreach($line as $value){
        if($value['springbreak'] === 'true'){
            echo $value['name'];
        }
    }
}

Answer 4

我想出了以下解决方案：

<?php

    $liste = [
        ['name' => 'Elsa', 'job' => 'Student', 'springbreak' => 'true' ],
        ['name' => 'Chris', 'job' => 'Teacher', 'springbreak' => 'true' ],
        ['name' => 'Zob', 'job' => 'Student', 'springbreak' => 'false' ],
        ['name' => 'Ken', 'job' => 'Teacher', 'springbreak' => 'true' ],
        ['name' => 'Ryan', 'job' => 'Student', 'springbreak' => 'false' ],
        ['name' => 'Tenta', 'job' => 'Teacher', 'springbreak' => 'true' ]

    ];


    $going_to_springbreak = array();

    //Check every item
    foreach($liste as $line){
        //Check first if the 'springbreak' is true
        if($line['springbreak'] == 'true'){
            //Then add the name of that item to the new array
            $going_to_springbreak[] = $line['name'];

            //OR you can add the entire item to the new array if you want to use the other values
            //$going_to_springbreak[] = $line;
        }
    }

    var_dump($going_to_springbreak)

?>

输出：

array(4) {
      [0]=>
      string(4) "Elsa"
      [1]=>
      string(5) "Chris"
      [2]=>
      string(3) "Ken"
      [3]=>
      string(5) "Tenta"
    } 

最后，我强烈建议将“真”或“假”值存储为原始值，因此：

'springbreak' => true