Push And Pull - PHP

This may come as a bit of a shock to you, but PHP's arrayfunctions can do a lot more than just count the elements of an array oriterate through key-value pairs. This article takes an in-depth look atPHP's less well-known array manipulation tools, illustrating how they canbe used to write tighter, more efficient code...and have some fun in thebargain as well!

TABLE OF CONTENTS:

By: Vikram Vaswani, (c) Melonfire

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November 09, 2001

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TOOLS YOU CAN USE

You can add an element to the end of an existing array with the array_push() function,

<?
// create array
$superheroes = array("spiderman", "superman", "captain marvel", "green
lantern");
array_push($superheroes, "the incredible hulk");
// $superheroes now contains ("spiderman", "superman", "captain marvel",
"green lantern", "the incredible hulk")
?>

and remove an element from the end with the interestingly-named array_pop() function.

<?
// create array
$superheroes = array("spiderman", "superman", "captain marvel", "green
lantern");
array_pop($superheroes);
// $superheroes now contains ("spiderman", "superman", "captain marvel")
?>

If you need to pop an element off the top of the array, you can use the array_shift() function,

<?
// create array
$superheroes = array("spiderman", "superman", "captain marvel", "green
lantern");
array_shift($superheroes);
// $superheroes now contains ("superman", "captain marvel", "green lantern")
?>

while the array_unshift() function takes care of adding elements to the beginning of the array.

<?
// create array
$superheroes = array("spiderman", "superman", "captain marvel", "green
lantern");
array_unshift($superheroes, "the human torch");
// $superheroes now contains ("the human torch", "spiderman", "superman",
"captain marvel", "green lantern")
?>

In case you need an array of a specific length, you can use the array_pad() function to create an array and pad it with empty elements (or elements containing a user-defined value). The following example should make this clearer:

<?
// create array
$students = array();
// returns an array containing 4 null values
$students = array_pad($students, 4, "");
?>

The second argument also specifies the direction of padding, while the third argument to the function specifies the value to be used for the empty elements.

<?
// create array
$desserts = array("chocolate mousse", "tiramisu", "apple pie", "chocolate
fudge cake", "apricot fritters");
// returns an array containing 8 elements
// ("chocolate mousse", "tiramisu", "apple pie", "chocolate fudge cake",
"apricot fritters", "dummy", "dummy", "dummy")
// array is padded to the right since the size is positive
$desserts = array_pad($desserts, 8, "dummy");
// this would return the same array, but padded to the left (note the
negative size)
// ("dummy", "dummy", "dummy", "chocolate mousse", "tiramisu", "apple pie",
"chocolate fudge cake", "apricot fritters")
$desserts = array_pad($desserts, -8, "dummy");
?>

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