PHP: How to filter array by specific key value range and keep key names?

How to filter a PHP array by a specific key value range and keep the key names? Follow these steps: Define a callback function that checks whether the key value is within the specified range. Call array_filter(), passing in the callback function and array as parameters.

PHP: How to filter an array by a specific key value range and keep the key names?

In PHP, we can use the array_filter() function to filter an array by a specific key value range while keeping the key names. This function accepts as argument a callback function that decides whether to retain each element in the array.

Callback function

The callback function should accept two parameters: key and value. It returns a Boolean value indicating whether the element should be retained.

Syntax

array_filter($array, $callback, $flag = 0);

Where:

• $array is the array to be filtered.
• $callback is a callback function that determines whether to retain each element in the array.
• $flag is an optional parameter that specifies how to index the elements in the array.

Example

Suppose we want to filter out elements with key values ​​within a specific range from an associative array. Here are the steps to achieve this:

1. Define a callback function that checks whether the key value is within the specified range.
2. Call array_filter(), passing the callback function and array as parameters.

Code

<?php

$array = [
    "a" => 1,
    "b" => 2,
    "c" => 3,
    "d" => 4,
    "e" => 5,
];

// 定义回调函数
$callback = function ($key, $value) {
    return $value >= 2 && $value <= 4;
};

// 按键值范围过滤数组
$filteredArray = array_filter($array, $callback);

// 输出结果
print_r($filteredArray);
?>

Output

Array
(
    [b] => 2
    [c] => 3
    [d] => 4
)

As you can see, the resulting array only contains the key value 2 to 4, and the key names are preserved.

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