Array functions in PHP8: various application examples of array_reduce()

Array function in PHP8: Various application examples of array_reduce()

In PHP, array is a very important data type, it can store multiple values, and various arrays can be used Functions perform operations and processing. Among them, the array_reduce() function is a very useful function. It can iteratively calculate all elements in an array into a single value and return that value.

The syntax of the array_reduce() function is as follows:

mixed array_reduce ( array $array , callable $callback [, mixed $initial = NULL ] )

Among them, the $array parameter is the array to be iteratively calculated, the $callback parameter is the function passed to each element in the array, and the $initial parameter is an optional initial value, which is used as the initial value of the accumulator when the $callback function is called for the first time.

The array_reduce() function is very flexible to use and can be used to process different types of arrays, and different $callback functions can be passed according to different needs. The following will introduce some common application examples of the array_reduce() function.

1. Calculate the sum of all elements in an array

This is one of the simplest applications of the array_reduce() function, used to calculate the sum of all elements in an array. You can use the built-in addition function as the $callback function, as follows:

$numbers = array(1, 2, 3, 4, 5);
$sum = array_reduce($numbers, 'addition ', 0);
function addition($a, $b) {

return $a + $b;

}
echo $sum; //Output: 15

2. Convert multiple Convert an array into an array

Sometimes you need to merge multiple arrays into one array. You can use the array_reduce() function to achieve this. You can use the built-in array_merge function as the $callback function as follows:

$arr1 = array('a', 'b', 'c');
$arr2 = array('d' , 'e', ​​'f');
$arr3 = array('g', 'h', 'i');
$arr ​​= array_reduce(array($arr1, $arr2, $arr3) , 'array_merge', array());
print_r($arr); //Output: Array ( [0] => a [1] => b [2] => c [3] = > d [4] => e [5] => f [6] => g [7] => h [8] => i )

3. Calculate array The product of all elements in an array

Calculating the product of all elements in an array is also one of the common applications of the array_reduce() function. You can use the built-in multiplication function as the $callback function, as follows:

$numbers = array(1, 2, 3, 4, 5);
$product = array_reduce($numbers, 'multiplication ', 1);
function multiplication($a, $b) {

return $a * $b;

}
echo $product; //Output: 120

4. put in the array String concatenation of elements

Conducting string concatenation of elements in an array is also an application of the array_reduce() function. You can use the built-in string_concatenate function as the $callback function, as follows:

$words = array('hello', 'world', 'php');
$sentence = array_reduce($words, 'string_concatenate');
function string_concatenate($a, $b) {

return $a . ' ' . $b;

}
echo $sentence; //Output: hello world php

5. Ask Get the number of occurrences of a certain element in the array

Sometimes you need to count the number of occurrences of a certain element in the array, you can use the array_reduce() function to achieve this. It should be noted that the $initial parameter should be set to 0, as follows:

$letters = array('a', 'b', 'c', 'a', 'c', 'a' , 'd');
$counts = array_reduce($letters, 'count_letters', array('a' => 0, 'b' => 0, 'c' => 0, 'd' => 0));
function count_letters($a, $b) {

if(isset($a[$b])) {
    $a[$b]++;
}
return $a;

}
print_r($counts); //Output: Array ( [a] => 3 [b] => 1 [c] => 2 [d] => 1 )

In the above example, an associative array is used to count the number of occurrences of each letter. If in the $callback function If $b exists in $a, add 1 to the value of $a[$b].

Summary

The above are just a few common application examples of the array_reduce() function, and the applications are flexible and diverse. When writing PHP programs, you can choose different application methods according to different needs, take advantage of the various advantages of the array_reduce() function, and achieve code efficiency and maintainability.

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