多维数组中的最小值和最大值

Question

嗨,我想找到x和y的最小值和最大值,我怎么能发现这个min和max函数不能正常工作

$dataPoints = array(
 array('x' => 2343, 'y' => 4322),
  array('x' => 103, 'y' => 303 ),
  array('x' => 2345,'y' => 2321 ),
  array('x' => 310, 'y' => 2044 ),
  array('x' => 173, 'y' => 793 ),
  array('x' => 456, 'y' => 2675),
  array('x' => 24, 'y' => 819 ));

Answer 1

我知道你必须编写自己的函数:

<?php  
    function max_with_key($array, $key) {
        if (!is_array($array) || count($array) == 0) return false;
        $max = $array[0][$key];
        foreach($array as $a) {
            if($a[$key] > $max) {
                $max = $a[$key];
            }
        }
        return $max;
    }


    $dataPoints = array(
     array('x' => 2343, 'y' => 4322),
      array('x' => 103, 'y' => 303 ),
      array('x' => 2345,'y' => 2321 ),
      array('x' => 310, 'y' => 2044 ),
      array('x' => 173, 'y' => 793 ),
      array('x' => 456, 'y' => 2675),
      array('x' => 24, 'y' => 819 ));

    $max_x = max_with_key($dataPoints, 'x');  //2343
    $max_y = max_with_key($dataPoints, 'y');  //4322
?>

Answer 2

您可以使用PHP的array_column()(PHP 5> = 5.5.0):

$min_x = min( array_column( $dataPoints, 'x' ) );
$min_y = min( array_column( $dataPoints, 'y' ) );
$max_x = max( array_column( $dataPoints, 'x' ) );
$max_x = max( array_column( $dataPoints, 'y' ) );

Answer 3

尝试这样的事情:

foreach($dataPoints as $point) {
    if (!isset($x) || $point['x'] > $x) {
        $x = $point['x'];
    }
    if (!isset($y) || $point['y'] > $y) {
        $y = $point['y'];
    }
}