How Can I Preserve Key Types When Merging Arrays in PHP?

Preserving Key Types During Array Merge in PHP

In PHP, you may encounter the need to combine two arrays while maintaining the original string and integer indices. However, the default array_merge() function reindexes the resulting array with consecutive integers.

Original Code with Issue

// Array with string-indexed pairs
$staticIdentifications = [
    'userID'   => 'USERID',
    'username' => 'USERNAME'
];

// Array with integer-indexed pairs
$companyVarIdentifications = CompanyVars::getIdentificationVarsFriendly($_SESSION['companyID']);

// Unsuccessful Attempt to Merge with Preserved Key Types
$idVars = array_merge($staticIdentifications, $companyVarIdentifications);

Solution: Array Addition

To preserve the key types during the merge, use the operator instead of array_merge():

$idVars = $staticIdentifications + $companyVarIdentifications;

This operation concatenates the two arrays while retaining their respective key types. The resulting $idVars array will contain both string and integer keys, reflecting the original structures of the input arrays.

Benefits of Array Addition

Unlike array_merge(), array addition:

• Preserves the original key types, crucial for maintaining the associations between keys and values.
• Avoids unexpected reindexing, which can break references to array elements based on their indices.
• Provides a simpler and more straightforward approach to array concatenation.

In this specific case, the $idVars array will have both string keys (e.g., 'userID') and integer keys (e.g., 123), enabling access to values based on both types of keys.

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