How to filter and filter elements in PHP arrays

How to filter and filter elements in PHP arrays

In PHP, arrays are a very commonly used data structure, and we often need to filter and filter elements of arrays. This article will introduce several commonly used methods and functions to filter and filter elements of PHP arrays.

1. Use the array_filter() function to filter

The array_filter() function is a built-in function in PHP, used to filter elements in an array. It accepts an array as input and returns a filtered array of results. We can decide whether to retain the elements in the array by passing a custom callback function.

The following is a sample code:

$numbers = array(1, 2, 3, 4, 5, 6);

// 过滤掉所有奇数
$filtered_numbers = array_filter($numbers, function ($number) {
    return $number % 2 == 0;
});

print_r($filtered_numbers);

The output result is:

Array
(
    [1] => 2
    [3] => 4
    [5] => 6
)

In the above example, we use an anonymous function as a callback function to determine whether a number is even. By calling the array_filter() function, we will filter out all odd numbers and keep only even numbers.

2. Use the array_map() function for filtering

The array_map() function is another commonly used array function, which can apply a callback function to each element in the array , and returns a new array. By setting filter conditions in the callback function, we can easily filter out the elements we need.

The following is a sample code:

$names = array("Alice", "Bob", "Charlie", "David");

// 筛选出名字长度大于等于5的人
$filtered_names = array_filter($names, function ($name) {
    return strlen($name) >= 5;
});

print_r($filtered_names);

The output result is:

Array
(
    [2] => Charlie
    [3] => David
)

In the above example, we use the strlen() function to get the length of the name, in the callback The function determines whether the length is greater than or equal to 5. By calling the array_filter() function, we filter out people whose names are longer than or equal to 5.

3. Use foreach loop to filter and filter

In addition to using built-in functions, we can also use foreach loop to manually filter and filter array elements. This approach is more flexible and can be customized to suit your needs.

The following is a sample code:

$ages = array(21, 18, 25, 16, 30);

// 过滤掉所有未成年人（年龄小于 18 岁）
$filtered_ages = array();
foreach ($ages as $age) {
    if ($age >= 18) {
        $filtered_ages[] = $age;
    }
}

print_r($filtered_ages);

The output result is:

Array
(
    [0] => 21
    [1] => 18
    [2] => 25
    [4] => 30
)

In the above example, we use a foreach loop to traverse the array and use if in the loop The statement determines whether the age is greater than or equal to 18 years old. If the condition is met, the element is added to the new array. Finally, we print out the filtered array.

Summary:

This article introduces several commonly used methods and functions to filter and filter elements of PHP arrays. Whether you use the built-in functions array_filter() and array_map(), or filter manually using a foreach loop, you can choose based on your specific needs. By mastering these methods, we can operate PHP arrays more flexibly and improve the readability and maintainability of the code.

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