When Can the Operator Safely Concatenate Arrays in PHP?

Understanding the Operator for Array Concatenation in PHP

In PHP, the operator can be employed to concatenate two arrays. However, certain cases may arise where this operator behaves unexpectedly, leading to incorrect results.

Consider the following code:

<code class="php">$array = array('Item 1');

$array += array('Item 2');

var_dump($array);</code>

The expected output would be an array containing both 'Item 1' and 'Item 2'. However, the actual output is:

array(1) {
  [0] => string(6) "Item 1"
}

This discrepancy occurs because PHP collapses array elements with duplicate keys when using the operator. In this case, both elements have a key of 0, resulting in only the first element being retained.

To address this issue and correctly concatenate arrays, it is recommended to utilize the array_merge() function instead.

<code class="php">$arr1 = array('foo');
$arr2 = array('bar');

// Will contain array('foo', 'bar');
$combined = array_merge($arr1, $arr2);</code>

Array_merge() preserves the array structure, ensuring that elements with different keys are correctly combined.

In scenarios where array elements possess unique keys, the operator can be an appropriate choice.

<code class="php">$arr1 = array('one' => 'foo');
$arr2 = array('two' => 'bar');

// Will contain array('one' => 'foo', 'two' => 'bar');
$combined = $arr1 + $arr2;</code>

The above is the detailed content of When Can the Operator Safely Concatenate Arrays in PHP?. For more information, please follow other related articles on the PHP Chinese website!