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If I want to use a PHP non-associative array like a dictionary and add a big key, how much memory will PHP allocate?
$myArray = Array();
$myArray[6000] = "string linked to ID 6000";
$myArray[7891] = "another key-value pair";
Will PHP also allocate memory for the unused keys 0-5999 and 6001-7890?
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2,147,483,647 items, even on 64-bit PHP. At least, the largest array you can have with array_fill() or range() appears to be 2^32-1 items. While keys can be anything, including numbers outside that range, if you start at zero, with a step size of 1, your highest index can be 2147483646.
Arrays in PHP is a type of data structure that allows us to store multiple elements of similar data type under a single variable thereby saving us the effort of creating a different variable for every data.
Numeric arrays allow us to store multiple values of the same data type in a single variable without having to create separate variables for each value. These values can then be accessed using an index which in case of numeric arrays is always a number. Note: By default the index always starts at zero.
To create an array, you use the array() construct: $myArray = array( values ); To create an indexed array, just list the array values inside the parentheses, separated by commas.
No, PHP doesn't implement this like a C style array. Php arrays are associative containers, as the php article on arrays states.
An array in PHP is actually an ordered map. A map is a type that associates values to keys.
Since order is preserved, the array will likely be some kind of binary search tree. If you're unfamiliar with binary search trees I suggest picking up a good data structures book to learn more or check out this wikipedia article for a rundown. Your example above would yield a binary search tree with two nodes -- one for data at key 6000, the other for key 7891.
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It won't allocate memory for indexes 0-5999.
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