How can the use of single quotes versus double quotes affect the interpretation of array keys in PHP, and what best practices should be followed?

Using single quotes versus double quotes in PHP can affect the interpretation of array keys. When using double quotes, PHP will evaluate any variables or special characters within the string, while single quotes will treat the string as a literal value. To ensure consistency and avoid unexpected behavior, it is best practice to use single quotes for array keys that do not require evaluation.

// Incorrect usage of double quotes for array keys
$array = [
    "key1" => "value1",
    "key2" => "value2",
];

// Corrected usage of single quotes for array keys
$array = [
    'key1' => 'value1',
    'key2' => 'value2',
];