创建数组后设置数组键值

Question

我正在尝试在创建数组后设置数组键的值。我知道这会，这确实给出了错误：

Notice: Undefined variable: peter in C:\web\apache\htdocs\test\array.php on line 144 Peter is years old.

$age=array("Peter"=>$ageVal);// Has to come first, since it's inside an include file.

$ageVal = 35; //Comes later.

echo "Peter is " . $age['Peter'] . " years old.";

但是有没有办法在不改变顺序的情况下这样做呢？ a）首先创建数组b）稍后设置数组键的值。

Answer 1

是的，你可以通过分配数组值by reference来做到这一点，虽然我不建议这样做。

这有效（但我不推荐）：

$age=array("Peter" => &$ageVal);// Has to come first, since it's inside an include file.

$ageVal = 35; //Comes later.

echo "Peter is " . $age['Peter'] . " years old.";

Demo

这是我推荐的方式：

$age = array(); // Comes first, since it's inside an include file.

$ageVal = 35; // Comes later.
$age['Peter'] = $ageVal; // Assigns a value to the 'Peter' key in $age

echo "Peter is " . $age['Peter'] . " years old.";

Answer 2

您可以在一行中设置两个变量。

$age['Peter'] = $ageVal = 35;

Answer 3

不要在顶部初始化数组。

$age=array();// Has to come first, since it's inside an include file.

$ageVal = 35; //Comes later.
$age['Peter'] = $ageval;  // Set the array element here.

echo "Peter is " . $age['Peter'] . " years old.";