PHP數組 並集 交集 差集

並集

array_merge

字符串鍵名相同，后面覆蓋前面，數字鍵名會在后面追加，不覆蓋，參考代碼如下

$array1 = array("color" => "red", 2, 4);
$array2 = array("a", "b", "color" => "green", "shape" => "trapezoid", 4);
$result = array_merge($array1, $array2);
print_r($result);

結果

Array ( [color] => green [0] => 2 [1] => 4 [2] => a [3] => b [shape] => trapezoid [4] => 4 )

如果鍵名都是數字的話，后面的數組元素會追加到前面數組之后，並重建索引

$array1 = array(1 => 2, 2 => 4, 3 => 6);
$array2 = array(1 => 1, 2 => 3, 3 => 5);
$result = array_merge($array1, $array2);
print_r($result);

結果

Array ( [0] => 2 [1] => 4 [2] => 6 [3] => 1 [4] => 3 [5] => 5 )

使用+運算符

使用+運算符合並數組，會保留前面數組的鍵名，后面數組元素會追加到前面數組后面，並且鍵名相同時，是前面覆蓋后面。

$array1 = array(0 => 'zero_a', 2 => 'two_a', 3 => 'three_a');
$array2 = array(1 => 'one_b', 3 => 'three_b', 4 => 'four_b');
$result = $array1 + $array2;
print_r($result);

結果

Array ( [0] => zero_a [2] => two_a [3] => three_a [1] => one_b [4] => four_b )

交集

array_intersect

第一個數組是主值，返回有相同元素的值（判斷依據是元素字符串相同，即 (string) $elem1 === (string) $elem2），鍵值保留第一個元素的鍵值

$array1 = array("a" => "green", "red", "blue");
$array2 = array("b" => "green", "yellow", "red");
$result = array_intersect($array1, $array2);
print_r($result);

結果

Array ( [a] => green [0] => red )

array_intersect_assoc

array_intersect_assoc不僅檢查元素值，還會檢查鍵名，都相同的元素才會保留下來，鍵值對 key => value 中的兩個值僅在 (string) $elem1 === (string) $elem2 時被認為相等

$array1 = array("a" => "green", "b" => "brown", "c" => "blue", "red", 100 => 'a100');
$array2 = array("a" => "green", "b" => "yellow", "blue", "red", '100' => 'a100');
$result_array = array_intersect_assoc($array1, $array2);
print_r($result_array);

結果

Array ( [a] => green [100] => a100 )

差集

array_diff

返回前面數組有而后面沒有的元素數組，保留前面元素的鍵名，相同判斷是根據字符串值相同，即 (string) $elem1 === (string) $elem2

$array1 = array("a" => "green", "red", "blue", "red");
$array2 = array("b" => "green", "yellow", "red");
$result = array_diff($array1, $array2);

print_r($result);

結果

Array ( [1] => blue )

array_diff_assoc

array_diff_assoc不僅檢查元素，還檢查鍵名，鍵值對 key => value 中的兩個值僅在 (string) $elem1 === (string) $elem2 時被認為相等

$array1 = array("a" => "green", "b" => "brown", "c" => "blue", "red");
$array2 = array("a" => "green", "yellow", "red");
$result = array_diff_assoc($array1, $array2);
print_r($result);

結果

Array ( [b] => brown [c] => blue [0] => red )

在來個例子

$array1 = array(0, 1, 2);
$array2 = array("00", "01", "2");
$result = array_diff_assoc($array1, $array2);
print_r($result);

結果

Array ( [0] => 0 [1] => 1 )