PHP：刪除特定數組之前的所有數組元素

Question

嗨，我有以下數組：

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

現在，我想做一個循環，自動刪除第4號之前的所有對象。
我嘗試了這個：

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

但這行不通。

Answer 1

將$ days更改為$ i，因為$ 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（）給出更短的解決方案：

$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);

回報

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

Answer 3

你的數組

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

循環刪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);

結果

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

如果希望索引再次從0開始，則可以使用array_values