Could you tell me your way to delete an item from array? Do you think it's good?
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3 Answers
That depends:
$a1 = array('a' => 1, 'b' => 2, 'c' => 3);
unset($a1['b']);
// array('a' => 1, 'c' => 3)
$a2 = array(1, 2, 3);
unset($a2[1]);
// array(0 => 1, 2 => 3)
// note the missing index 1
// solution 1 for numeric arrays
$a3 = array(1, 2, 3);
array_splice($a3, 1, 1);
// array(0 => 1, 1 => 3)
// index is now continous
// solution 2 for numeric arrays
$a4 = array(1, 2, 3);
unset($a4[1]);
$a4 = array_values($a4);
// array(0 => 1, 1 => 3)
// index is now continous
Generally unset() is safe for hashtables (string-indexed arrays), but if you have to rely on continous numeric indexes you'll have to use either array_splice() or a combination of unset() and array_values().
2 Comments
John
Why would you use unset combined with array_values rather than array_splice?
Stefan Gehrig
@John: One scenario I can think about is, when you want to remove several items from one array. With the
unset()-way you can remove the values without having to think about changing keys - if you're done your run the array through array_values() to normalize the indexing. That's cleaner and faster than using array_splice() several times.The common way:
According to the manual
unset($arr[5]); // This removes the element from the array
The filtered way:
There is also the array_filter() function to take care of filtering arrays
$numeric_data = array_filter($data, "is_numeric");
To get a sequential index you can use
$numeric_data = array_values($numeric_data);
References
PHP – Delete selected items from an array
Comments
It depends. If want to remove an element without causing gaps in the indexes, you need to use array_splice:
$a = array('a','b','c', 'd');
array_splice($a, 2, 1);
var_dump($a);
Output:
array(3) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[2]=>
string(1) "d"
}
Using unset can work, but this results in a non-continuous index. This can sometimes be a problem when you iterate over the array using count($a) - 1 as a measure of the upper bound:
$a = array('a','b','c', 'd');
unset($a[2]);
var_dump($a);
Output:
array(3) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[3]=>
string(1) "d"
}
As you see, count is now 3 but the index of the last element is also 3.
My recommendation is therefore to use array_splice for arrays with numerical indexes, and use unset only for arrays (dictionaries really) with non-numerical indexes.
1 Comment
nickf
alternatively you could call
unset($a[2]); $a = array_values($a);