php array_map array_filter sort

array_map — Applies the callback to the elements of the given arrays （处理映射）

array_filter — Filters elements of an array using a callback function      （过滤）

<?php
function cube($n)
{
    return($n * $n * $n);
}

$a = array(1, 2, 3, 4, 5);
$b = array_map("cube", $a);
print_r($b);
?>

Array
(
    [0] => 1
    [1] => 8
    [2] => 27
    [3] => 64
    [4] => 125
)

array_filter()没有回调函数的时候，可以过滤数组中值为空的值例如：

<?php

$entry = array(
             0 => 'foo',
             1 => false,
             2 => -1,
             3 => null,
             4 => ''
          );

print_r(array_filter($entry));
?>

Array
(
    [0] => foo
    [2] => -1
)

sort   This function sorts an array. Elements will be arranged from lowest to highest when this function has completed.

<?php

$fruits = array("lemon", "orange", "banana", "apple");
sort($fruits);
foreach ($fruits as $key => $val) {
    echo "fruits[" . $key . "] = " . $val . "\n";
}

?>

fruits[0] = apple
fruits[1] = banana
fruits[2] = lemon
fruits[3] = orange