Solving problems encountered in using the PHP function array_udiff function

Solution to problems encountered when using PHP function array_udiff function

<?php
// array_udiff()
class Obj
{
	private $code = 0;

	public function construct($code)
	{
		$this->code = intval($code);
	}

	public function getCode()
	{
		return $this->code;
	}

	/**
	 * 该函数必须根据实际情况返回 0, 1, -1 这三种值，才能正确计算出差集
	 */
	public static function cmp($a, $b)
	{
		if ($a->getCode() === $b->getCode()) return 0;
		return $a->getCode() > $b->getCode() ? 1 : -1;
	}

	/**
	 * 此种形式是在《深入PHP面向对象模式与实践》一书看到的写法
	 * 经验证是无效的，具体在第十章讲解组合模式处
	 */
	public static function cmp2($a, $b)
	{
		return $a === $b ? 0 : 1;
	}
}

$e1 = new Obj(&#39;111&#39;);
$e2 = new Obj(&#39;222&#39;);
$e3 = new Obj(&#39;333&#39;);
$e4 = new Obj(&#39;444&#39;);
$e5 = new Obj(&#39;555&#39;);
$e6 = new Obj(&#39;666&#39;);

$arr = [$e1, $e2, $e3, $e4, $e5, $e6];
$arr2 = [$e2, $e3, $e6];

$arr = array_udiff($arr, $arr2, [&#39;Obj&#39;, &#39;cmp&#39;]);
// $arr = array_udiff($arr, $arr2, [&#39;Obj&#39;, &#39;cmp2&#39;]); // cmp2 这个比较方法无法返回正确结果
var_dump($arr);

array_diff Notes on usage:

1. Return difference Centralized, the key names remain unchanged

2. Two units are considered the same only when (string) $elem1 === (string) $elem2 of. That is, when the expression of string is the same.

Similar functions:

array_diff_assoc
array_diff_uassoc
array_diff_key
array_diff_ukey
array_udiff_assoc
array_udiff_uassoc

Summary:

##array_diff, array_udiff is judged only based on value

array_diff_key, array_diff_ukey is judged based on key only

array_diff_assoc, array_diff_uassoc, array_udiff_assoc, array_udiff_uassoc is judged based on key and value together

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