Question

我有一个关联数组和一组键。

$A = array('a'=>'book', 'b'=>'pencil', 'c'=>'pen');
$B = array('a', 'b');

如何从$A的所有元素构建一个关联数组，其中键位于$B？对于上面的例子，答案应该是

$C = array('a'=>'book', 'b'=>'pencil');

Answer 1

$keys = array_flip($B);
$C = array_intersect_key($A,$keys);

Answer 2

array_intersect_key($A,array_combine($B,$B))

或更好：array_intersect_key($my_array, array_flip($allowed))

来自问题：PHP: How to use array_filter() to filter array keys?

Answer 3

这是一个简单的解决方案，可以在将密钥附加到$A之前检查密钥是否存在于$C

$A = array('a'=>'book', 'b'=>'pencil', 'c'=>'pen');
$B = array('a', 'b');

$C = array();
foreach ($B as $bval) {
  // If the $B key exists in $A, add it to $C
  if (isset($A[$bval])) $C[$bval] = $A[$bval];
}

var_dump($C);

// Prints:
array(2) {
  ["a"]=>
  string(4) "book"
  ["b"]=>
  string(6) "pencil"
}

Answer 4

$keys = array_keys($B);
$C = array();
foreach ($A as $key => $value)
{
  if (in_array($key, $keys))
  {
    $C[$key] = $value;
  }
}

Answer 5

令我惊讶的是，foreach循环方法更快。

以下快速基准测试脚本为我提供了结果： array_intersect_key: 0.76424908638 foreach loop: 0.6393928527832

$A = array('a'=>'book', 'b'=>'pencil', 'c'=>'pen');
$B = array('a', 'b');

$start = microtime(true);
for ($i = 0 ; $i < 1000000; $i++) {
$c = array_intersect_key($A,array_flip($B));
}

$t1 = microtime(true);

for ($i = 0; $i < 1000000; $i++) {
$C = array();
    foreach ($B as $bval) {
          // If the $B key exists in $A, add it to $C
          if (isset($A[$bval])) $C[$bval] = $A[$bval];
    }
}

$t2 = microtime(true);
echo "array_intersect_key: " . ($t1 - $start), "\n";
echo "foreach loop: " . ($t2 - $t1), "\n";

如何使用PHP中的键数组过滤关联数组？

5 个答案: