Foreach循环的奇怪行为

Question

I am experiencing some strange behaviour with the following foreach loop. I am running it on PHP 5.3.0.

print_r($this->form_spec['fields']);
foreach($this->form_spec['fields'] as $f=>$field) {
     print_r($this->form_spec['fields']);                      
}

The first print_r prints the following (note: I've excluded a bunch of keys to make my point clearer):

Array
(      
    [0] => Array
    (
       [field_name] => d_first_name
    )

    [1] => Array
        (
            [field_name] => d_last_name
        )
)

The second print_r prints:

Array
(
    [0] => Array
        (
            [field_name] => d_first_name
        )

    [1] => Array
        (
            [field_name] => d_first_name
        )
)

$this->form_spec['fields'] already has it's values before it reaches the for each loop. The first print_r shows the correct values. Then the second print_r shows that the values have changed. There is no other code between these.

Could it be a bug in 5.3.0?

The only way I could get round the problem was by using a for loop instead, but the Foreach SHOULD work, it always has done before. Can anybody enlighten me?

[EDIT] Just to clarify, the bug is that the contents of $this->form_spec['fields'] changes not the fact that I can't print properly.

Answer 1

You are printing $this->form_spec['fields'] instead of the result of the iteration $field .

EDIT

Now that I can see what you mean. It looks like you are changing the contents of the object while iterating over it somewhere in your loop. Could you please post the relevant code?

I'm 99% sure there is more code which is touched while iterating which changes what you have.

Answer 2

You should be doing this:-

print_r($this->form_spec['fields']);
foreach($this->form_spec['fields'] as $f=>$field) {
     print_r($field);                      
}

I have run this test on your code:-

for($i = 0; $i < 10; $i++){
    $form_spec['fields'][] = array('field_name' => 'field_' . $i);
}
print_r($form_spec['fields']);
foreach($form_spec['fields'] as $f => $field) {
    print_r($form_spec['fields']);
}

(PHP_VERSION = 5.3.0)

and got the output I expected, so you must be altering that array somewhere. You need to check your code very carefully.

Output:-

Array
(
    [0] => Array
        (
            [field_name] => field_0
        )

    [1] => Array
        (
            [field_name] => field_1
        )

    [2] => Array
        (
            [field_name] => field_2
        )

    [3] => Array
        (
            [field_name] => field_3
        )

    [4] => Array
        (
            [field_name] => field_4
        )

    [5] => Array
        (
            [field_name] => field_5
        )

    [6] => Array
        (
            [field_name] => field_6
        )

    [7] => Array
        (
            [field_name] => field_7
        )

    [8] => Array
        (
            [field_name] => field_8
        )

    [9] => Array
        (
            [field_name] => field_9
        )

)

Repeated 10 times.