How to modify the key value in an array in php? 4 methods introduced

PHP is a very popular and convenient programming language that supports array types. In PHP, array is a very commonly used data type that can be used to store and operate multiple data. When we need to modify the key value of an element in an array, PHP also provides a variety of methods to achieve this. In this article, we will introduce various methods of modifying key values ​​​​in arrays in PHP.

1. Use the array_combine() and array_keys() methods

The array_combine() method can use the value of an array as the key value of a new array, and array_keys() The method is used to obtain all keys in an array. Therefore, we can use the two methods together to update the key value by modifying the value in the array.

The example is as follows:

<?php $arr = array(&#39;a&#39;=>1, 'b'=>2, 'c'=>3);

$new_keys = array('d', 'e', 'f');

$new_arr = array_combine($new_keys, $arr);

print_r($new_arr);
?>

The running result is:

Array ( [d] => 1 [e] => 2 [f] => 3 )

In the above example, we use the array_combine() method to combine the new key value array $new_keys and the original array$ arr merge, achieving the purpose of modifying the key value.

2. Use the foreach() method to loop through the array

Using the foreach() method can easily traverse the array. We can use this method to modify the corresponding key values ​​while traversing the array.

The example is as follows:

<?php $arr = array(&#39;a&#39;=>1, 'b'=>2, 'c'=>3);

foreach($arr as $key => $value) {
    if($value == 1) {
        $arr[$key] = 'new_key';
    }
}

print_r($arr);
?>

The running result is:

Array ( [new_key] => 1 [b] => 2 [c] => 3 )

In the above example, we use the foreach() method to loop through the array, when an element with a value of 1 is found , modify its key value to 'new_key'.

3. Use the array_map() method

The array_map() method can use a callback function to process each element in the array. Therefore, we can modify it by returning a new key value in this function.

The example is as follows:

<?php $arr = array(&#39;a&#39;=>1, 'b'=>2, 'c'=>3);

$new_arr = array_map(function($value){
    if($value == 1) {
        return 'new_key';
    } else {
        return $value;
    }
}, $arr);

print_r($new_arr);
?>

The running result is:

Array ( [new_key] => 1 [b] => 2 [c] => 3 )

In the above example, we use the array_map() method to process each element in the array through the callback function. When an element with value 1 is found, its key value is modified to 'new_key'.

4. Use the array_walk() method

The array_walk() method can traverse each element in the array, and then call the callback function for each element to modify it.

The example is as follows:

<?php $arr = array(&#39;a&#39;=>1, 'b'=>2, 'c'=>3);

function change_key(&$value, $key)
{
    if($value == 1) {
        $value = 'new_key';
    }
}

array_walk($arr, 'change_key');

print_r($arr);
?>

The running result is:

Array ( [new_key] => 1 [b] => 2 [c] => 3 )

In the above example, we traverse each element in the array through the array_walk() method and call the callback function change_key () to modify the key value in the array.

To sum up, there are many ways to modify the key values ​​in an array in PHP, including using the array_combine() and array_keys() methods, using the foreach() method to loop through the array, using the array_map() method, and using array_walk() method and so on. Different functions can be achieved using different methods, and developers can choose the appropriate method according to their own needs.

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