Function

Explanation

Example

sizeof($arr)

This
function returns the number of elements in an array.

Use
this function to find out how many elements an array contains; this
information is most commonly used to initialize a loop counter when
processing the array.

array_values($arr)

This
function accepts a PHP array and returns a new array containing only its
values (not its keys). Its counterpart is the array_keys() function.

Use
this function to retrieve all the values from an associative array.

array_keys($arr)

This
function accepts a PHP array and returns a new array containing only its keys
(not its values). Its counterpart is the array_values() function.

Use
this function to retrieve all the keys from an associative array.

array_pop($arr)

This
function removes an element from the end of an array.

array_push($arr, $val)

This
function adds an element to the end of an array.

array_shift($arr)

This
function removes an element from the beginning of an array.

array_unshift($arr, $val)

This
function adds an element to the beginning of an array.

each($arr)

This
function is most often used to iteratively traverse an array. Each time each() is called,
it returns the current key-value pair and moves the array cursor forward one
element. This makes it most suitable for use in a loop.

sort($arr)

This
function sorts the elements of an array in ascending order. String values
will be arranged in ascending alphabetical order.

Note: Other
sorting functions include asort(), arsort(),
ksort(), krsort() and rsort().

array_flip($arr)

The
function exchanges the keys and values of a PHP associative array.

Use
this function if you have a tabular (rows and columns) structure in an array,
and you want to interchange the rows and columns.

array_reverse($arr)

The
function reverses the order of elements in an array.

Use
this function to re-order a sorted list of values in reverse for easier
processing—for example, when you're trying to begin with the minimum or
maximum of a set of ordered values.

array_merge($arr)

This
function merges two or more arrays to create a single composite array. Key
collisions are resolved in favor of the latest entry.

Use
this function when you need to combine data from two or more arrays into a
single structure—for example, records from two different SQL queries.

array_rand($arr)

This
function selects one or more random elements from an array.

Use
this function when you need to randomly select from a collection of discrete
values—for example, picking a random color from a list.

array_search($search,
$arr)

This
function searches the values in an array for a match to the search term, and
returns the corresponding key if found. If more than one match exists, the
key of the first matching value is returned.

Use
this function to scan a set of index-value pairs for matches, and return the
matching index.

array_slice($arr, $offset, $length)

This
function is useful to extract a subset of the elements of an array, as
another array. Extracting begins from array offset $offset and
continues until the array slice is $length elements long.

Use
this function to break a larger array into smaller ones—for example, when
segmenting an array by size ("chunking") or type of data.

array_unique($data)

This
function strips an array of duplicate values.

Use
this function when you need to remove non-unique elements from an array—for
example, when creating an array to hold values for a table's primary key.

array_walk($arr, $func)

This
function "walks" through an array, applying a user-defined function
to every element. It returns the changed array.

Use
this function if you need to perform custom processing on every element of an
array—for example, reducing a number series by 10%.