Thought I'd add to the discussion since I believe there exists a crucial difference between the two when working with indexed arrays that people should be aware of.
Say you are dynamically creating a multi-dimensional associative array by looping through some data sets.
$foo = []
foreach ($fooData as $fooKey => $fooValue) {
foreach ($fooValue ?? [] as $barKey => $barValue) {
// Approach 1: results in Error 500
array_push($foo[$fooKey], $barKey); // Error 500: Argument #1 ($array) must be of type array
// NOTE: ($foo[$fooKey] ?? []) argument won't work since only variables can be passed by reference
// Approach 2: fix problem by instantiating array beforehand if it didn't exist
$foo[$fooKey] ??= [];
array_push($foo[$fooKey], $barKey);
// Approach 3: One liner approach
$foo[$fooKey][] = $barKey; // Instantiates array if it doesn't exist
}
}
Without having $foo[$fooKey]
instantiated as an array beforehand, we won't be able to do array_push
without getting the Error 500
. The shorthand $foo[$fooKey][]
does the heavy work for us, checking if the provided element is an array, and if it isn't, it creates it and pushes the item in for us.