There are several sort functions for arrays in php:

sort()

Sort an array in ascending order by value.

$fruits = ['Zitrone', 'Orange', 'Banane', 'Apfel'];
sort($fruits);
print_r($fruits);

results in

Array
(
    [0] => Apfel
    [1] => Banane
    [2] => Orange
    [3] => Zitrone
)

rsort()

Sort an array in descending order by value.

$fruits = ['Zitrone', 'Orange', 'Banane', 'Apfel'];
rsort($fruits);
print_r($fruits);

results in

Array
(
    [0] => Zitrone
    [1] => Orange
    [2] => Banane
    [3] => Apfel
)

asort()

Sort an array in ascending order by value and preserve the indecies.

$fruits = [1 => 'lemon', 2 => 'orange',  3 => 'banana', 4 => 'apple'];
asort($fruits);
print_r($fruits);

results in

Array
(
    [4] => apple
    [3] => banana
    [1] => lemon
    [2] => orange
)

arsort()

Sort an array in descending order by value and preserve the indecies.

$fruits = [1 => 'lemon', 2 => 'orange',  3 => 'banana', 4 => 'apple'];
arsort($fruits);
print_r($fruits);

results in