How to create an empty array in PHP with predefined size?
You can't predefine a size of an array in php. A good way to acheive your goal is the following:
// Create a new array.
$array = array();
// Add an item while $i < yourWantedItemQuantity
for ($i = 0; $i < $number_of_items; $i++)
{
array_push($array, $some_data);
//or $array[] = $some_data; for single items.
}
Note that it is way faster to use array_fill() to fill an Array :
$array = array_fill(0,$number_of_items, $some_data);
If you want to verify if a value has been set at an index, you should use the following: array_key_exists("key", $array) or isset($array["key"])
See array_key_exists , isset and array_fill
PHP Arrays don't need to be declared with a size.
An array in PHP is actually an ordered map
You also shouldn't get a warning/notice using code like the example you have shown. The common Notice people get is "Undefined offset" when reading from an array.
A way to counter this is to check with isset
or array_key_exists
, or to use a function such as:
function isset_or($array, $key, $default = NULL) {
return isset($array[$key]) ? $array[$key] : $default;
}
So that you can avoid the repeated code.
Note: isset
returns false if the element in the array is NULL, but has a performance gain over array_key_exists
.
If you want to specify an array with a size for performance reasons, look at:
SplFixedArray in the Standard PHP Library.
There is no way to create an array of a predefined size without also supplying values for the elements of that array.
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.
Potentially relevant- if you want to initialize and fill an array with a range of values, use PHP's (wait for it...) range function:
$a = range(1, 5); // array(1,2,3,4,5)
$a = range(0, 10, 2); // array(0,2,4,6,8,10)