Quick methods to change the array structure: array_map, array_reduce, etc.

Arrays are frequently used data structures in programming, and when processing arrays, changing their structures is a common requirement. In the PHP language, there are many built-in functions that can be used to accomplish this purpose, such as array_map, array_reduce, etc. This article will introduce and practical applications of these functions.

array_map

array_map function is a variable function in PHP (variable function means that you can use variables as function names in the code). This function is used to convert all the elements in an array Elements are converted by the specified callback function and a new array is returned. The number and order of elements in the new array are consistent with the original array.

Syntax: array_map(callback,array1,array2...)

• callback: required, specifies the callback function. In the callback function, a variable name must be specified for each parameter, and a value should be returned with return.
• array1: required, specifies the array.
• array2...: Optional, specifies the array.

Example 1:

$a = [1,2,3,4,5];

function square($n)
{
    return $n * $n;
}

$b = array_map("square", $a);

print_r($b);

Output result: Array ( [0] => 1 [1] => 4 [2] => 9 [3 ] => 16 [4] => 25 )

Example 2:

$a1 = [1,2,3];
$a2 = ['one', 'two', 'three'];

function combine($n1, $n2)
{
    return $n1 . $n2;
}

$b = array_map("combine", $a1, $a2);

print_r($b);

Output result: Array ( [0] => 1one [1] => 2two [2] => 3three )

array_reduce

The array_reduce function is used to iterate all elements in the array one by one by specifying a callback function and return a single value.

Syntax: array_reduce (array, callback, [initial_value])

• array: required, specifies the array.
• callback: required, specified function. The function accepts two parameters: the result of the previous iteration and the current element.
• initial_value: Optional, specifies the first value used for logical processing.

Example one:

$a = [1, 2, 3, 4, 5];

$sum = array_reduce($a, function($total, $num){
    return $total + $num;
});

echo $sum;

Output result: 15

Example two:

$a = ['Hello', 'World', '!'];

$sentence = array_reduce($a, function($sentence, $word){
    return $sentence . ' ' . $word;
});

echo $sentence;

Output result: Hello World!

Summary

array_map and array_reduce functions are very practical array traversal functions. They can help us quickly change the structure of the array to meet our needs. Everyone can apply it flexibly in development and make practical applications based on their own needs.

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