PHP foreach循环不适用于嵌套数组

Question

I have no idea why this isn't working. I've tried everything. I'm sure I'm missing something.

Here's the array:

$userList = array('first_name'=>array('John','Jane'), 'last_name'=>array('Smith','Doe'));

The for loop works, I do get a proper output:

$usercount = count($userList);  
for($i=0; $i < $usercount; $i++) {  
echo $userList['first_name'][$i];  
}

But this foreach loop doesn't:

foreach($userList as $user) {  
echo $user['first_name'];  
echo $user['last_name'];  
}

What should I do? What's wrong with the code?

Answer 1

There are no first_name or last_name keys in your inner arrays. What $user contains is array('John','Jane') respectively array('Smith','Doe') .

What you probably want though is a structure like:

$userList = array(
    array('first_name' => 'John', 'last_name' => 'Smith'), 
    array('first_name' => 'Jane', 'last_name' => 'Doe')
);

That allows you to use the foreach you allready have.

Answer 2

The foreach approach isn't going to give you the desired output because of the way your array is structured:

foreach($userList as $user) {
    //$user is array('John', 'Jane') on the first iteration
}

You could update your array to look like this:

array(
    array('first_name' => 'John', 'last_name' => 'Smith'),
    array('first_name' => 'Jane', 'last_name' => 'Doe')
);

Your foreach loop should work with the array structured like that.

Answer 3

If you do print_r($userList); the output is

Array
(
    [first_name] => Array
        (
            [0] => John
            [1] => Jane
        )

    [last_name] => Array
        (
            [0] => Smith
            [1] => Doe
        )
)

As you can see, you are storing all of the first names in one array and all of the last names in another array. I think you meant to store each user in their own array.

To do that, you need something like

 $userList = array(array("first_name" => "John", "last_name" => "Doe"), array("first_name" => "Jane", "last_name" => "Doe"));

Now if you print_r($userList); it will output:

Array
(
    [0] => Array
        (
            [first_name] => John
            [last_name] => Doe
        )

    [1] => Array
        (
            [first_name] => Jane
            [last_name] => Doe
        )

)

Which your foreach statement should correctly iterate through.