Assign key of an array element to a variable - php

Question

I have the following piece of code and inside the function field_has_input(), I would like to assign the element's key to the errors[]
i.e. errors[]=$key instead of errors[]=$field
The function field_has_input($field) gets called from check_all_fields($_POST)
Hopefully someone can help out.
function field_has_input($field)
{
global $errors;
if(!isset($field) || empty($field))
{
$errors[]=$field;
}
}
function check_all_fields($_POST)
{
global $errors;
foreach($_POST as $key => $value)
{
echo $_POST[$key] . "<br />";
field_has_input($_POST[$key]);
}
//exit;
var_dump($errors);
return $errors;
}

Answer 1

I would suggest you dispense with the field_has_input() function entirely, and just do the work inside the other loop. Otherwise, you would need to be passing the $key into the inner function. In its current simplicity it is totally unnecessary and adds complexity.
function check_all_fields($_POST)
{
global $errors;
foreach($_POST as $key => $value)
{
// empty() calls isset() implicitly...
if (empty($value)) {
$errors[] = $key;
}
}
//exit;
var_dump($errors);
return $errors;
}
Further, I would recommend not using the global errors, but instead passing it to the function. Because $_POST is a superglobal, it is unnecessary to pass it as a parameter to your function. Pass only $errors instead.
function check_all_fields($errors) {
// $_POST is already available here...
foreach($_POST as $key => $value)
{
if (empty($value)) {
$errors[] = $key;
}
}
return $errors;
}
If you must use an inner function, such as if the actual work to be done in field_has_input() is more complex than just checking empty(), pass the $key and check $_POST[$key] inside the function
function field_has_input($key, $errors) {
if (empty($_POST[$key])) {
$errors[] = $key;
}
}

Answer 2

If you want to get an array of values consisting of the $_POST keys that are empty, you can do that with just one line:
$errors = array_keys( array_diff_key( $_POST, array_filter($_POST) ) );
array_filter will remove false, null or empty string values
array_diff_key will compare the original full post array to the filtered version and return only the keys that have been filtered.
array_keys will create an array of values using the array keys of the given array
Example, if:
$arr = array (
'name' => 'Bob'
,'company' => ''
,'state' => 'CA'
,'phone' => ''
);
$errors = array_keys( array_diff_key( $arr, array_filter($arr) ) );
var_dump($errors);
// output:
array(2) {
[0]=>
string(7) "company"
[1]=>
string(5) "phone"
}