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7.2.5 Removing and Inserting Elements in an Array

The array_splice( ) function can remove or insert elements in an array:
$removed = array_splice(array, start [, length [, replacement ] ]);
We’ll look at array_splice( ) using this array:
$subjects = array(‘physics’, ‘chem’, ‘math’, ‘bio’, ‘cs’, ‘drama’, ‘classics’);

We can remove the math, bio, and cs elements by telling array_splice( ) to start at position 2
and remove 3 elements:

$removed = array_splice($subjects, 2, 3); // $removed is array(‘math’, ‘bio’, ‘cs’) // $subjects
is array(‘physics’, ‘chem’);

If you omit the length, array_splice( ) removes to the end of the array:
$removed = array_splice($subjects, 2); // $removed is array(‘math’, ‘bio’, ‘cs’, ‘drama’, ‘classics’)
// $subjects is array(‘physics’, ‘chem’);

If you simply want to delete the elements and you don’t care about their values, you don’t need
to assign the results of array_splice( ):

array_splice($subjects, 2); // $subjects is array(‘physics’, ‘chem’);
To insert elements where others were removed, use the fourth argument:
$new = array(‘law’, ‘business’, ‘IS’); array_splice($subjects, 4, 3, $new); // $subjects is
array(‘physics’, ‘chem’, ‘math’, ‘bio’, ‘law’, ‘business’, ‘IS’)
The size of the replacement array doesn’t have to be the same as the number of elements you
delete. The array grows or shrinks as needed:
$new = array(‘law’, ‘business’, ‘IS’); array_splice($subjects, 2, 4, $new); // $subjects is
array(‘physics’, ‘chem’, ‘math’, ‘law’, ‘business’, ‘IS’)
To get the effect of inserting new elements into the array, delete zero elements:

$subjects = array(‘physics’, ‘chem’, ‘math’);
$new = array(‘law’, ‘business’);
array_splice($subjects, 2, 0, $new); // $subjects is array(‘physics’, ‘chem’, ‘law’, ‘business’, ‘math’)
Although the examples so far have used an indexed array, array_splice( ) also works on
associative arrays:
$capitals = array(‘India’ => ‘New Delhi’, ‘Great Britain’ => ‘London’, ‘New Zealand’ =>
‘Wellington’, ‘Australia’ => ‘Canberra’, ‘Italy’ => ‘Rome’);
$down_under = array_splice($capitals, 2, 2); // remove New Zealand and Australia $france =
array(‘France’ => ‘Paris’);
array_splice($capitals, 1, 0, $france); // insert France between USA and G.B.

Before PHP 4.3.0, appending to an array in which the current maximum key
was negative would create a new key. Since PHP 4.3.0, the new key will be 0.

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