PHP：删除特定数组之前的所有数组元素

Question

嗨，我有以下数组：

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

现在，我想做一个循环，自动删除第4号之前的所有对象。
我尝试了这个：

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

但这行不通。

Answer 1

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);

Answer 2

可以使用array_slice（）给出更短的解决方案：

$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);

回报

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

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
)

如果希望索引再次从0开始，则可以使用array_values