There are over 70 array functions available in PHP, but listed below are 40 of the most useful (and understandable) functions.

Function	Description
array()	Create an array
array_change_key_case()	Changes all keys in an array
array_chunk()	Split an array into chunks
array_combine()	Creates an array by using one array for keys and another for its values
array_count_values()	Counts all the values of an array
array_flip()	Exchanges all keys with their associated values in an array
array_keys()	Return all the keys or a subset of the keys of an array
array_merge()	Merge one or more arrays
array_multisort()	Sort multiple or multi-dimensional arrays
array_pad()	Pad array to the specified length with a value
array_product()	Calculate the product of values in an array
array_rand()	Pick one or more random entries out of an array
array_reverse()	Return an array with elements in reverse order
array_search()	Searches the array for a given value and returns the corresponding key if successful
array_slice()	Extract a slice of the array
array_splice()	Remove a portion of the array and replace it with something else
array_sum()	Calculate the sum of values in an array
array_unique()	Removes duplicate values from an array
arsort()	Sort an array in reverse order and maintain index association
asort()	Sort an array and maintain index association
compact()	Create array containing variables and their values
count()	Count all elements in an array, or properties in an object
current()	Return the current element in an array
each()	Return the current key and value pair from an array and advance the array cursor
end()	Set the internal pointer of an array to its last element
in_array()	Checks if a value exists in an array
is_array()	Checks if a variable is an array
key()	Fetch a key from an array
krsort()	Sort an array by key in reverse order
ksort()	Sort an array by key
list()	Assign variables as if they were an array
natcasesort()	Sort an array using a case insensitive "natural order" algorithm
natsort()	Sort an array using a "natural order" algorithm
next()	Advance the internal array pointer of an array
prev()	Rewind the internal array pointer
range()	Create an array containing a range of elements
reset()	Set the internal pointer of an array to its first element
rsort()	Sort an array in reverse order
shuffle()	Shuffle an array
sizeof()	Alias of count
sort()	Sort an array

Each function accepts different arguments in order to produce its result. They are all documented in the official PHP manual, but we will run through a few common example here.

The sort() function accepts a single argument (the array name) and re-arranges each value in that array from lowest to highest, or in alphabetical order. If the array is an associative array, the existing keys will be removed and numerical keys will be assigned in their place. If the array is already numerical, the number keys will simply be re-arranged.

The count() function will return how many elements (values) there are in an array.

The range() function creates an array containing a range of numbers between the two numbers specified as arguments. If a third numerical argument is presented, it is used as the unit of incrementation. The default third argument is 1.

Let's take a look at these three functions in action.

<?php
  $fruit = array("orange", "pineapple", "peach", "apple", "pear", "cherry");

  sort($fruit);
  print_r($fruit);

  echo count($fruit);

  $range_array = range(0, 50, 5);
  print_r($range_array);
?>

And the results are:

Array ( [0] => apple [1] => cherry [2] => orange [3] => peach [4] => pear [5] => pineapple )

6

Array ( [0] => 0 [1] => 5 [2] => 10 [3] => 15 [4] => 20 [5] => 25 [6] => 30 [7] => 35 [8] => 40 [9] => 45 [10] => 50 )

Assignment: Use shuffle() to mix up the fruit array, then use array_search() to determine which key that the value "pineapple" ends up under, and echo "pineapple" from the result of the search.