PHP：删除特定元素之前的所有数组元素

Question

你好，我有以下数组：

$days = array(
            1=>"Sunday",
            2=>"Monday",
            3=>"Tuesday",
            4=>"Wednesday",
            5=>"Thursday",
            6=>"Friday",
            7=>"Saturday"
            );

现在我想创建一个循环，自动删除所有编号为4之前的对象。
我尝试了以下代码：

$startIndex = 4;
for($i = 1; $days < $startIndex; $i++)
{
    unset($days[$i]);
}

但它无法正常工作。

- coder

---

дЅ зњ‹иї‡array_splice吗？例如：array_splice($days, 0, 4); - Professor Abronsius

Answer 1

可以使用array_slice()函数来简化解决方案：

$days = array(
            1=>"Sunday",
            2=>"Monday",
            3=>"Tuesday",
            4=>"Wednesday",
            5=>"Thursday",
            6=>"Friday",
            7=>"Saturday"
            );


$startIndex = 4;
$days = array_slice($days, $startIndex-1, NULL, TRUE);

print_r($days);

返回结果

Array
(
    [4] => Wednesday
    [5] => Thursday
    [6] => Friday
    [7] => Saturday
)

- syck

Answer 2

将$days更改为$i，因为$i是您的索引值。

$days = array(
            1=>"Sunday",
            2=>"Monday",
            3=>"Tuesday",
            4=>"Wednesday",
            5=>"Thursday",
            6=>"Friday",
            7=>"Saturday"
            );


$startIndex = 4;
for($i = 1; $i < $startIndex; $i++)
{
    unset($days[$i]);
}

print_r($days);

- Marcin

Answer 3

你的数组

$days = array
(
     1=>"Sunday",
     2=>"Monday",
     3=>"Tuesday",
     4=>"Wednesday",
     5=>"Thursday",
     6=>"Friday",
     7=>"Saturday"
);

循环删除指定索引之前的所有元素。

# Number to stop the unset.
$split_number =4;
# Loop through array

for($a=0;$a<sizeof($days);$a++)
{
    if($a < $split_number)
        # Unset element if condition is true
        unset($days[$a]);
}

print_r($days);

结果

Array
(
    [4] => Wednesday
    [5] => Thursday
    [6] => Friday
    [7] => Saturday
)

如果您希望索引再次从0开始，可以使用array_values函数。

- André Ferraz