Question

I have this kind of array:

   $a = array(
    'one' => 'one',
    '0' => '0',
    'two' => 'two',
    'three' => 'three',
    'four'              
   );

as you can see it is an associative array BUT not all the keys have the value (take a look at the last).
My question is, how can i loop this kind of array to get key(if exists) and the respective value?

Thank you!

Answer 1

The string 'four' in your example is not a key but a value. The corresponding key will be 1. This happens because PHP converts the string key '0' to numeric key 0 and for the value 'four' it uses the next numeric key which will be 1.

Reference:

A key may be either an integer or a string. If a key is the standard
representation of an integer, it will be interpreted as such (i.e. “8”
will be interpreted as 8, while “08” will be interpreted as “08”)

To have a key with no value you can use NULL as the value:

'four'  => null

Similarly to have an empty key use null as key:

null => 'four'

And to loop over such an array you can use a foreach loop. To detect if a key/value is null or not you can use the isset function.