How to merge arrays in php to remove duplicate data

In PHP programming, array is a very commonly used data structure. In many cases, we need to merge two or more arrays and remove duplicate elements. This article will introduce how to implement this function.

1. Array merging

PHP provides some functions to complete array merging operations. The most commonly used one is the array_merge() function.

Code example:

$a = array('a', 'b', 'c');
$b = array('d', 'e', 'f');
$c = array_merge($a, $b);
print_r($c);

Output result:

Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
    [4] => e
    [5] => f
)

2. Remove duplicate elements

When there are duplicate elements in the array, we It may be necessary to remove duplicate elements and keep only one of them. This function can be implemented using PHP's array_unique() function.

Code example:

$a = array('a', 'b', 'c', 'a', 'c');
$b = array_unique($a);
print_r($b);

Output result:

Array
(
    [0] => a
    [1] => b
    [2] => c
)

3. Merge and remove duplicate elements

If we need to combine two arrays To merge and remove duplicate elements, you can use the above two functions together.

Code example:

$a = array('a', 'b', 'c');
$b = array('c', 'd', 'e');
$c = array_merge($a, $b);
$d = array_unique($c);
print_r($d);

Output result:

Array
(
    [0] => a
    [1] => b
    [2] => c
    [4] => d
    [5] => e
)

4. Customize sorting and remove duplicate elements

Sometimes we may need Customize the sorting of the array, such as sorting by the length of the element value. This function can be implemented using PHP's usort() function. Combining usort() with array_unique() can implement custom sorting and remove duplicate elements.

Code example:

$a = array('aaa', 'aa', 'aaaaa', 'a', 'aaaa');
usort($a, function($a, $b) {
    return strlen($a) < strlen($b);
});
$b = array_unique($a);
print_r($b);

Output result:

Array
(
    [0] => aaaa
    [2] => aaaaa
    [1] => aaa
)

5. Summary

In PHP programming, array merging and deduplication are A very important operation. PHP provides a rich function library to implement these functions. In actual use, it is necessary to choose the appropriate function according to the specific situation to make the program more efficient and concise.

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