php array_diff_ukey() array_diff_uassoc() 理解

<?php
if ('ab'>'b') {
echo a;
} else {
echo b;
}

?>

<?php
function key_compare_func($key1, $key2)
{
if ($key1 == $key2)
return 0;
else if ($key1 > $key2)
return 1;
else
return -1;
}

$array1 = array('blue'  => 1, 'red'  => 2, 'green'  => 3, 'purple' => 4);
$array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan'   => 8);

var_dump(array_diff_ukey($array1, $array2, 'key_compare_func'));
?>

array(2) {
["red"]=>
int(2)
["purple"]=>
int(4)
}

<?php
function key_compare_func($key1, $key2)
{
if ($key1 == $key2)
return 1;
else if ($key1 > $key2)
return 0;
else
return -1;
}

$array1 = array('blue'  => 1, 'red'  => 2, 'green'  => 3, 'purple' => 4);
$array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan'   => 8);

var_dump(array_diff_ukey($array1, $array2, 'key_compare_func'));
?>

array(1) {
["blue"]=>
int(1)
}