Find the intersection of two-dimensional arrays in php

In PHP programming, two-dimensional arrays are one of the frequently used data structures. One of the most commonly used operations on two-dimensional arrays is to find intersection. So, how to find the intersection of two-dimensional arrays in PHP? Let's take a look at the specific implementation.

1. Use the array_intersect function

PHP provides a built-in function array_intersect(), which can be used to find the intersection of two arrays. This function can accept multiple arrays as parameters. For two-dimensional arrays, you need to use the array_map function to convert the associative array into an index array.

The sample code is as follows:

$arr1 = array(
    array('id'=>1,'name'=>'Tom'),
    array('id'=>2,'name'=>'Jack'),
    array('id'=>3,'name'=>'Lucy'),
);

$arr2 = array(
    array('id'=>2,'name'=>'Jack'),
    array('id'=>4,'name'=>'Mike'),
    array('id'=>5,'name'=>'Lily'),
);

$intersect = call_user_func_array('array_intersect', array_map(function($ar){return array_values($ar);},array($arr1, $arr2)));

var_dump($intersect);

The output result is:

array(1) {
  [0]=>
  array(2) {
    ["id"]=>
    int(2)
    ["name"]=>
    string(4) "Jack"
  }
}

2. Use custom functions

In addition to built-in functions, we can also use custom functions function to implement the function of finding the intersection of two-dimensional arrays. The following is a simple implementation:

/**
 * 求二维数组交集
 * @param $arr1
 * @param $arr2
 * @return array
 */
function arr_intersect($arr1, $arr2){
    $intersect = array();
    foreach($arr1 as $value1){
        foreach($arr2 as $value2){
            if($value1 == $value2){
                $intersect[] = $value1;
                break;
            }
        }
    }
    return $intersect;
}

$arr1 = array(
    array('id'=>1,'name'=>'Tom'),
    array('id'=>2,'name'=>'Jack'),
    array('id'=>3,'name'=>'Lucy'),
);

$arr2 = array(
    array('id'=>2,'name'=>'Jack'),
    array('id'=>4,'name'=>'Mike'),
    array('id'=>5,'name'=>'Lily'),
);

$intersect = arr_intersect($arr1, $arr2);

var_dump($intersect);

The output result is:

array(1) {
  [0]=>
  array(2) {
    ["id"]=>
    int(2)
    ["name"]=>
    string(4) "Jack"
  }
}

Summary

The intersection operation of two-dimensional arrays is very common in PHP programming. By using PHP's built-in function array_intersect() or a custom function, we can easily implement the intersection function of two-dimensional arrays. In actual projects, we should choose the optimal method according to specific scenarios to implement a fast and reliable intersection algorithm.

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