How to Create an Empty Array in PHP with Predefined Size

How to create an empty array in PHP with predefined size?

There is no way to create an array of a predefined size without also supplying values for the elements of that array.

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The best way to initialize an array like that is array_fill. By far preferable over the various loop-and-insert solutions.

$my_array = array_fill(0, $size_of_the_array, $some_data);

Every position in the $my_array will contain $some_data.

The first zero in array_fill just indicates the index from where the array needs to be filled with the value.

In php how do I set the size of an array?

Use SplFixedArray for a fixed-size array:

$array = new SplFixedArray(3);
$array[0] = 1;
$array[1] = 2;
$array[2] = 3;
$array[3] = 4; // RuntimeException

Is there a PHP equivalent of new Array (number) in javascript?

Actually, in this context, you're creating an array of size 13.

You don't really need to preallocate arrays in PHP, but you can do something like:

$result = array_fill( 0, 12, null);

This will create an array with 13 elements (indexes 0 through 12) whose values are null.

Best way to initialize (empty) array in PHP

In ECMAScript implementations (for instance, ActionScript or JavaScript), Array() is a constructor function and [] is part of the array literal grammar. Both are optimized and executed in completely different ways, with the literal grammar not being dogged by the overhead of calling a function.

PHP, on the other hand, has language constructs that may look like functions but aren't treated as such. Even with PHP 5.4, which supports [] as an alternative, there is no difference in overhead because, as far as the compiler/parser is concerned, they are completely synonymous.

// Before 5.4, you could only write
$array = array(
    "foo" => "bar",
    "bar" => "foo",
);

// As of PHP 5.4, the following is synonymous with the above
$array = [
    "foo" => "bar",
    "bar" => "foo",
];

If you need to support older versions of PHP, use the former syntax. There's also an argument for readability but, being a long-time JS developer, the latter seems rather natural to me.  I actually made the mistake of trying to initialise arrays using [] when I was first learning PHP.

This change to the language was originally proposed and rejected due to a majority vote against by core developers with the following reason:

This patch will not be accepted because slight majority of the core developers voted against. Though if you take a accumulated mean between core developers and userland votes seems to show the opposite it would be irresponsible to submit a patch witch is not supported or maintained in the long run.

However, it appears there was a change of heart leading up to 5.4, perhaps influenced by the implementations of support for popular databases like MongoDB (which use ECMAScript syntax).

Quickly create large arrays in PHP

In PHP, you don't have to predefine the size of your array, you can dynamically append it with data, like so:

$bar = array();
for($i = 0;$i < 50;$i++) {
    $bar[] = $i;
}

By calling the $bar with [], you'll indicate that a new key should be created and in this case hold value $i.

How to initialize an empty array of object with a predefined array?

Use a map:

var newArray = admins.map((admin) => ({ name: admin }));

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