PHP array_filter() 函数

<?php
$array1 = ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5];
$array2 = [6, 7, 8, 9, 10, 11, 12];
echo "Odd :<br />";
print_r(array_filter($array1, "odd"));
echo "<br />";
echo "Even:<br />";
print_r(array_filter($array2, "even"));
function odd($var)
{
    // 返回输入整数是否为奇数（单数）
    return $var & 1;
}
function even($var)
{
    // 返回输入整数是否为偶数
    return !($var & 1);
}
?>

<?php
$entry = [
    0 => 'foo',
    1 => false,
    2 => -1,
    3 => null,
    4 => '',
    5 => '0',
    6 => 0,
];
print_r(array_filter($entry));
?>