仅输出部分基于初始字符的数组

Question

我有一个数组$myArr['words']，它包含以下格式的数据：

Array (
[above-the-fold] => Array
  (
    [term] => Above the fold
    [desc] => The region of a Web ...
  )

[active-voice] => Array
  (
    [term] => Active voice
    [desc] => Makes subjects do ...
  )

[backlinks] => Array
  (
    [term] => Backlinks
    [desc] => Used on content ....
  )
)

我输出的内容如下：

foreach($myArr['words'] as $k => $v) {
  echo '
  <a href="#'.$k.'">
    '.$v['term'].'
  </a>';
}

如何添加约束以输出仅以特定字符开头的值$k。例如：

$ltr = 'a';

Answer 1

$test = ['abc'=>'1', 'def'=>'2', 'deh'=>'3'];

foreach($test as $k => $v){
    if($k[0] == 'd') {
        echo $v . "\r\n";
    }
}

https://3v4l.org/e7I8m

Answer 2

您还可以使用更灵活的方法:通过正则表达式进行匹配。

<?php

$myArr = [
    'zzzz' => [
        'term' => 'zuzuzu',
        'desc' => 'zazaza ...'
    ],
    'above-the-fold' => [
        'term' => 'Above the fold',
        'desc' => 'The region of a Web ...'
    ],
    'active-voice' => [
        'term' => 'Active voice',
        'desc' => 'Makes subjects do ...'
    ],
    'backlinks' => [
        'term' => 'Backlinks',
        'desc' => 'Used on content ....'
    ]
];

$reg = "/^a/";   // Key starts with "a" 

foreach (preg_grep($reg, array_keys($myArr)) as $k => $v)
    echo "<a href=\"#$v\" title=\"{$myArr[$v]['desc']}\">{$myArr[$v]['term']}</a>\n";

回声：

<a href="#above-the-fold" title="The region of a Web ...">Above the fold</a>
<a href="#active-voice" title="Makes subjects do ...">Active voice</a>

在线PHP的实例化

https://www.php.net/manual/en/function.preg-grep.php

https://www.php.net/manual/en/function.array-keys.php

Answer 3

您可以检查0位置的键：

if(strpos($k, 'a') === 0) {
    //echo
}

//or

if($k[0] === 'a') {
    //echo
}

或者在foreach上过滤数组和$result

$result = array_filter($myArr['words'],
                       function($v) { return $v[0] === 'a'; },
                       ARRAY_FILTER_USE_KEY);