The relationship between PHP array intersection and union and set theory

In PHP, array intersection uses the array_intersect() function to extract common elements to create a new array; union uses the array_merge() function to merge multiple array elements into a new array. This is similar to the concepts of intersection and union in set theory: intersection extracts common elements, and union combines all elements, effectively handling array set operations.

PHP The relationship between array intersection, union and set theory

In mathematical set theory, intersection and union are two an important concept. In PHP, arrays can also be viewed as sets, so intersection and union operations can also be used.

Intersection (array_intersect)

Intersection refers to extracting common elements from two arrays and creating a new array. Intersection can be achieved using the array_intersect() function.

Grammar:

array_intersect(array1, array2, ..., arrayN);

Practical case:

$array1 = [1, 2, 3, 4, 5];
$array2 = [3, 4, 5, 6, 7];
$intersection = array_intersect($array1, $array2);

// 输出交集：
print_r($intersection); // [3, 4, 5]

Union (array_merge)

Union refers to merging all elements in two or more arrays into a new array. Union can be achieved using the array_merge() function.

Grammar:

array_merge(array1, array2, ..., arrayN);

Practical case:

$array1 = [1, 2, 3, 4, 5];
$array2 = [3, 4, 5, 6, 7];
$union = array_merge($array1, $array2);

// 输出并集：
print_r($union); // [1, 2, 3, 4, 5, 6, 7]

Relationship with set theory

The intersection and union of arrays have a similar relationship to the intersection and union in set theory:

• Intersection: Extract the common elements in the two sets to form one New collection.
• Union: Merge all elements in two or more sets to form a new set.

Master the intersection and union operations of arrays, you can effectively process array collections, and perform efficient data filtering, extraction and merging operations.

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