Share six easy-to-use PHP array Array functions_php examples

这篇文章给大家分享六个比较好用的php数组Array函数，非常不错，具有一定的参考借鉴价值，需要的朋友参考下吧

1. array_column 返回输入数组中某个单一列的值。
2. array_filter 用回调函数过滤数组中的元素。
3. array_map 将用户自定义函数作用到给定数组的每个值上，返回新的值。
4. array_walk_recursive 对数组中的每个成员递归地应用用户函数。
5. extract (从数组中将变量导入到当前的符号表),  compact (创建一个包含变量名和它们的值的数组)
6. uasort 使用用户自定义的比较函数对数组中的键值进行排序。

1. array_column 返回输入数组中某个单一列的值。

类似功能有

1.1 Yii2 中的 ArrayHelper::index($array, 'id');

1.2 Yii2 中的 $query->select(['last_name', 'id'])->indexBy('id')->column();

// 可能从数据库中返回数组
$a = array(
 array(
  'id' => 5698,
  'first_name' => 'Peter',
  'last_name' => 'Griffin',
 ),
 array(
  'id' => 4767,
  'first_name' => 'Ben',
  'last_name' => 'Smith',
 ),
 array(
  'id' => 3809,
  'first_name' => 'Joe',
  'last_name' => 'Doe',
 )
);
$last_names = array_column($a, 'last_name', 'id');
print_r($last_names);

输出结果:

Array
(
    [5698] => Griffin
    [4767] => Smith
    [3809] => Doe
)

2. array_filter 用回调函数过滤数组中的元素。

function test_odd($var)
{
  return($var & 1);
}
$a1=array("a","b",2,3,4);
print_r(array_filter($a1,"test_odd"));

输出:

Array
(
    [2] => 2
    [3] => 3
    [4] => 4
)

3. array_map 将用户自定义函数作用到给定数组的每个值上，返回新的值。

此函数有点类似与 array_walk_recursive , 只是多写了一步递归

 function myfunction($v) {
   if (is_array($v)) {
     return array_map("myfunction", $v);
   }
  return($v * $v);
} 
 $a = array(1, 2, 3, 4, 5, 6 => [2, 3]);
print_r(array_map("myfunction", $a));

输出:

Array(    
[0] => 1    
[1] => 4    
[2] => 9    
[3] => 16    
[4] => 25    
[6] => Array([0] => 4 [1] => 9)
)

 function myfunction($v1, $v2) {
  if ($v1 === $v2) {
     return "same";
   }
   return "different";
 } 
 $a1 = array("Horse", "Dog", "Cat");
 $a2 = array("Cow", "Dog", "Rat");
 print_r(array_map("myfunction", $a1, $a2));

输出:

Array(    
[0] => different    
[1] => same    
[2] => different
)

4. array_walk_recursive 对数组中的每个成员递归地应用用户函数。

此函数有点类似与 array_map, 只是省去了写递归

 function myfunction(&$value, $key, $p) {
   if ($value == 'xxx') {
     $value = $p;
   }
 }
 $a = array("a" => "red", "b" => "green", "c" => "blue", 'd' => ['x' => 'xxx', 'y' => 'yyy']);
 array_walk_recursive($a, "myfunction", 'green');
 print_r($a);

输出:

Array(    
[a] => red    
[b] => green    
[c] => blue    
[d] => Array([x] => green [y] => yyy)
)

5. extract (从数组中将变量导入到当前的符号表),  compact (创建一个包含变量名和它们的值的数组)

 $a = "Original";
$my_array = array("a" => "Cat","b" => "Dog", "c" => "Horse");
 extract($my_array);
 echo "\$a = $a; \$b = $b; \$c = $c";

输出:

$a = Cat; $b = Dog; $c = Horse

 $firstname = "Peter";
 $lastname = "Griffin";
 $age = "41";
$result = compact("firstname", "lastname", "age");
 print_r($result);

输出:

Array
(
    [firstname] => Peter
    [lastname] => Griffin
    [age] => 41
)

6. uasort 使用用户自定义的比较函数对数组中的键值进行排序(可以对二维数组排序)。

$arr2 = [
  [
    'id' => 3,
    'age' => 33,
  ],
  [
    'id' => 2,
    'age' => 44,
  ],
  [
    'id' => 1,
    'age' => 22,
  ],
];
//按age字段升序排序
uasort($arr2, function($a, $b) {
  $field = 'age';
  if ($a[$field] == $b[$field]){
    return 0;
  }
  return ($a[$field] < $b[$field]) ? -1 : 1;
});
print_r($arr2);

输出:

Array(    
        [2] => Array([id] => 1 [age] => 22  )
    [0] => Array([id] => 3 [age] => 33   )
    [1] => Array([id] => 2  [age] => 44   )
)

The above is the detailed content of Share six easy-to-use PHP array Array functions_php examples. For more information, please follow other related articles on the PHP Chinese website!