How to avoid key name overwrite problem in array_combine()?

In PHP, the array_combine() function is used to combine two arrays into an associative array, one of which provides the key name and the other provides the corresponding value. It seems like this is a simple and straightforward function, but in some cases using array_combine() can cause problems with key names being overwritten. This problem usually occurs when duplicates exist in keyname arrays.

Basic usage of array_combine()

First, let’s take a look at the basic usage example of array_combine() :

 <?php
$keys = ['a', 'b', 'c'];
$values = [1, 2, 3];

$result = array_combine($keys, $values);
print_r($result);
?>

Output result:

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

As can be seen from the above code, array_combine() works properly. It combines the key name array $keys and the value array $values , returning a new associative array.

Risk of key names being overwritten

If the $keys array contains duplicate key names, array_combine() will overwrite the previous key-value pair. Let’s take a look at an example:

 <?php
$keys = ['a', 'b', 'b'];
$values = [1, 2, 3];

$result = array_combine($keys, $values);
print_r($result);
?>

Output result:

 Array
(
    [a] => 1
    [b] => 3
)

In this example, the 'b' key name appears repeatedly, resulting in the final result that only 'b' => 3 is preserved, and the original 'b' => 2 is overwritten.

How to avoid key names being overwritten?

To avoid this kind of key name overridden, we can take the following methods:

1. Check whether the key name is duplicated

Before using array_combine() , we can use array_count_values() to check whether there are duplicates in the key name array. If there are duplicates, you can first process the duplicate key name (for example, adding a suffix, etc.).

 <?php
$keys = ['a', 'b', 'b'];
$values = [1, 2, 3];

// Check if there are duplicates in the key name array
$keys_count = array_count_values($keys);
foreach ($keys_count as $key => $count) {
    if ($count > 1) {
        // Add a suffix to duplicate key names
        $keys = array_map(function($item) use ($key) {
            return $item === $key ? $key . '_dup' : $item;
        }, $keys);
    }
}

$result = array_combine($keys, $values);
print_r($result);
?>

Output result:

 Array
(
    [a] => 1
    [b_dup] => 2
    [b] => 3
)

In this way, we avoid the problem of overwriting the key names, and duplicate key names are added with the _dup suffix.

2. Use array_merge() to merge arrays

Another way is to use array_merge() for processing before merging. We can process duplicate key names when merging. For example, overwriting can be avoided by adding a random number or a unique identifier to the key name.

 <?php
$keys = ['a', 'b', 'b'];
$values = [1, 2, 3];

$keys = array_map(function($key) {
    return $key . uniqid('_'); // Add a unique identifier to duplicate key names
}, $keys);

$result = array_combine($keys, $values);
print_r($result);
?>

Output result:

 Array
(
    [a] => 1
    [b_6434e34d27e85] => 2
    [b_6434e34d27e86] => 3
)

In this way, we avoid the overriding of key names, and each duplicate key name is given a unique identifier.

Summarize

When using array_combine() , duplicate key names can cause overwrite issues. To avoid this problem, we can:

1. Check whether there are duplicates in the key name array. If there are duplicates, you can modify the key name to avoid overwriting.

2. Use array_merge() to merge arrays and process duplicate key names, such as adding a unique identifier.

Through these methods, you can ensure that the use of the array_combine() function does not cause the problem of the key name being overwritten.