How to delete specified items in array in php

PHP is a widely used open source server-side scripting language, which is used to develop web applications, dynamic websites, database connections, etc. In PHP, an array is an important data structure that can store multiple values ​​and can be easily accessed, added, modified, and deleted. In the actual development process, we often need to delete an element in the array or specify all elements with the same key value. This article will introduce how to delete a specified key in an array using PHP.

1. Overview of PHP arrays

In PHP, an array is an ordered, iterable collection that can store multiple values, each value has a unique key. PHP arrays can be divided into the following types:

1. Index array: Use integer keys (starting from 0) as indexes, and the storage order and insertion order are the same.

2. Associative array: Use custom string or numeric keys as indexes, and the relationship between keys and values ​​can be freely defined.

3. Multidimensional array: An array contains other arrays, which can form a multi-level nested structure.

The creation method of PHP array is relatively flexible, you can use the keyword array() or [], you can also use the range() function, explode() function, etc.

//使用array()创建索引数组
$arr1 = array('apple', 'banana', 'orange');
//使用[]创建关联数组
$arr2 = ['name' => 'Jack', 'age' => 18, 'gender' => 'male'];
//使用range()函数创建索引数组
$arr3 = range(1, 10);
//使用explode()函数创建索引数组
$str = "apple,banana,orange";
$arr4 = explode(",", $str);

?>

2. Delete the element with the specified index key in the array

If you want to delete an element in the PHP array element, you can use the unset() function, which can delete a variable, including elements in the array and attributes of the object. The unset() function needs to pass in a parameter, which can be a variable, array element or object property.

$arr = array('apple', 'banana', 'orange');
unset($arr[1]); //删除索引为1的元素banana
var_dump($arr); //array(2) { [0]=> string(5) "apple" [2]=> string(6) "orange" }

?>

In the above example, we created an index array $arr and deleted the index using the unset() function The element banana is 1, and then uses the var_dump() function to print out the deleted array.

It should be noted that using the unset() function can only delete the element with the specified index key, but not the specified key-value pair. If you want to delete elements of a specified key-value pair, you can use the array_diff() function to achieve this.

3. Delete the elements of the specified key-value pair in the array

If you want to delete the specified key-value pair in the PHP array, you can use the array_diff() function. The array_diff() function is used to calculate the difference of an array. If the elements in the array also exist in another array, they will not be included in the result array. Therefore, we can implement the deletion operation by passing the key-value pair to be deleted as an array to the array_diff() function.

$arr = ['name' => 'Jack', 'age' => 18, 'gender' => 'male'];
$remove = ['age' => 18];
$result = array_diff($arr, $remove);
var_dump($result); //array(2) { ["name"]=> string(4) "Jack" ["gender"]=> string(4) "male" }

?>

In the above example, we create an associative array $arr and use a new array $remove to Stores the key-value pairs to be deleted. By calling the array_diff() function, the key-value pair to be deleted is passed in as an array, and the returned result array does not contain the elements to be deleted.

For deletion of multi-dimensional arrays, we can use recursive functions.

function removeKey($array, $key)
{
    foreach ($array as $k => &$v) {
        if ($k=== $key) {
            unset($array[$k]);
        } else {
            if (is_array($v)) {
              $v = removeKey($v, $key);
            }
        }
    }
    return $array;
}

$arr = [
    'fruit' => ['apple', 'banana', 'orange'],
    'color' => [
        'red'   => 'FF0000',
        'green' => '00FF00',
        'blue'  => '0000FF'
    ]
];
$result = removeKey($arr, 'apple');
var_dump($result);

?>

In the above example, we defined a function removeKey(), which receives two parameters, the first The parameters are multidimensional arrays and the second parameter is the key to be deleted. In the function body, we use a foreach loop to traverse the array and judge each key-value pair. If the key is not equal to the key to be deleted, continue to traverse; if the key is equal to the key to be deleted, use the unset() function to remove the key from the array. Delete the key-value pair. If the value is an array, the removeKey() function is called recursively. Finally, the deleted array is returned.

4. Summary

This article introduces how to delete elements with specified keys and elements with specified key-value pairs in an array in PHP. For indexed arrays, we can use the unset() function to delete elements of specified index keys; for associative arrays, we can use the array_diff() function to delete elements of specified key-value pairs; for multi-dimensional arrays, we can use recursive functions to delete specified keys. Elements. When we need to modify or reconstruct a PHP array, we can use these methods to delete specified elements.

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