根据您的要求“每个值只能出现一次”，如果您只是想在数组中保持唯一的值，那么array_unique()可能就是您正在寻找的。

输入:

$input = array(4, "4", "3", 4, 3, "3");
$result = array_unique($input);
var_dump($result);

结果:

array(2) {
  [0] => int(4)
  [2] => string(1) "3"
}

function array_remove_by_value($array, $value)
{
    return array_values(array_diff($array, array($value)));
}

$array = array(312, 401, 1599, 3);

$newarray = array_remove_by_value($array, 401);

print_r($newarray);

输出

Array ([0] => 312 [1] => 1599 [2] => 3)

一个有趣的方法是使用array_keys():

foreach (array_keys($messages, 401, true) as $key) {
    unset($messages[$key]);
}

array_keys()函数接受两个额外的参数，只返回特定值的键，以及是否需要严格检查(即使用===进行比较)。

这也可以删除具有相同值的多个数组项(例如[1,2,3,3,4])。

你可以:

unset($messages[array_flip($messages)['401']]);

解释:在翻转数组后删除键为401的元素。

我认为最简单的方法是使用带有foreach循环的函数:

//This functions deletes the elements of an array $original that are equivalent to the value $del_val
//The function works by reference, which means that the actual array used as parameter will be modified.

function delete_value(&$original, $del_val)
{
    //make a copy of the original, to avoid problems of modifying an array that is being currently iterated through
    $copy = $original;
    foreach ($original as $key => $value)
    {
        //for each value evaluate if it is equivalent to the one to be deleted, and if it is capture its key name.
        if($del_val === $value) $del_key[] = $key;
    };
    //If there was a value found, delete all its instances
    if($del_key !== null)
    {
        foreach ($del_key as $dk_i)
        {
            unset($original[$dk_i]);
        };
        //optional reordering of the keys. WARNING: only use it with arrays with numeric indexes!
        /*
        $copy = $original;
        $original = array();
        foreach ($copy as $value) {
            $original[] = $value;
        };
        */
        //the value was found and deleted
        return true;
    };
    //The value was not found, nothing was deleted
    return false;
};

$original = array(0,1,2,3,4,5,6,7,4);
$del_val = 4;
var_dump($original);
delete_value($original, $del_val);
var_dump($original);

输出将是:

array(9) {
  [0]=>
  int(0)
  [1]=>
  int(1)
  [2]=>
  int(2)
  [3]=>
  int(3)
  [4]=>
  int(4)
  [5]=>
  int(5)
  [6]=>
  int(6)
  [7]=>
  int(7)
  [8]=>
  int(4)
}
array(7) {
  [0]=>
  int(0)
  [1]=>
  int(1)
  [2]=>
  int(2)
  [3]=>
  int(3)
  [5]=>
  int(5)
  [6]=>
  int(6)
  [7]=>
  int(7)
}

在PHP 7.4中使用箭头函数:

$messages = array_filter($messages, fn ($m) => $m != $del_val);

为了保持它是一个非关联数组，用array_values()来包装它:

$messages = array_values(array_filter($messages, fn ($m) => $m != $del_val));