An existing array can be modified by explicitly setting values
in it.
This is done by assigning values to the array, specifying the
key in brackets. The key can also be omitted, resulting in an empty pair of
brackets ([]).
$arr[key] = value; $arr[] = value; // key may be an integer or string // value may be any value of any type
If $arr doesn't exist yet, it will be created, so this is
also an alternative way to create an array. This practice is
however discouraged because if $arr already contains
some value (e.g. string from request variable) then this
value will stay in the place and [] may actually stand
for string access
operator. It is always better to initialize variable by a direct
assignment.
To change a certain
value, assign a new value to that element using its key. To remove a
key/value pair, call the unset() function on it.
<?php
$arr = array(5 => 1, 12 => 2);
$arr[] = 56; // This is the same as $arr[13] = 56;
// at this point of the script
$arr["x"] = 42; // This adds a new element to
// the array with key "x"
unset($arr[5]); // This removes the element from the array
unset($arr); // This deletes the whole array?>
As mentioned above, if no key is specified, the maximum of the existing
integer indices is taken, and the new key will be that maximum
value plus 1 (but at least 0). If no integer indices exist yet, the key will
be 0 (zero).
Note that the maximum integer key used for this need not
currently exist in the array. It need only have
existed in the array at some time since the last time the
array was re-indexed. The following example illustrates:
<?php// Create a simple array.$array = array(1, 2, 3, 4, 5);print_r($array);
// Now delete every item, but leave the array itself intact:foreach ($array as $i => $value) {
unset($array[$i]);
}print_r($array);
// Append an item (note that the new key is 5, instead of 0).$array[] = 6;print_r($array);
// Re-index:$array = array_values($array);$array[] = 7;print_r($array);?>
The above example will output:
Array
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
)
Array
(
)
Array
(
[5] => 6
)
Array
(
[0] => 6
[1] => 7
)
Strings
