Under what circumstances would
$array[$index] = $element;
and
unset($array[$index]);
$array[$index] = $element;
be different?
Assuming I am not using any references in my array, are these logically equivalent?
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4 Answers
If $index isn't numeric second variant would always append element to the end of array, so the order of keys will be changed.
Comments
unset($array[$index]);
would raise an E_NOTICE if $index is not found within $array. Other than that it looks the same.
Comments
The order is changed if you first remove a key and then add it again:
$arr = array("foo1" => "bar1", "foo2" => "bar2");
$arr["foo1"] = "baz";
print_r($arr);
$arr = array("foo1" => "bar1", "foo2" => "bar2");
unset($arr["foo1"]);
$arr["foo1"] = "baz";
print_r($arr);
Output:
Array
(
[foo1] => baz
[foo2] => bar2
)
Array
(
[foo2] => bar2
[foo1] => baz
)
Comments
if you need to know is exist there before assigning (isset) is useful use "unset", but these simply add a step to "unset".
for example:
if ($array[$index]=="a")
unset($array[$index]);
...
if (!isset($array[$index]))
$array[$index] = $element;
