a php function to check a 'deep' array value

Question

I've just coded a little function to check and get a deep array value. Basically, I need to return the value or null if it's not set or does not exists, or in general not useful for databases records. I need to check things like $myarray[key1][key2][key3] etc..

function get_array_deep_value(array $array, array $fields){
 $value = $array;
 foreach($fields as $field){
 $v = $value[$field] ?? null;
 if(empty($v) && $v != 0){ // note: using != operator because it will convert '0' to 0 (while !== does not)
 $value = null; 
 break;
 } 
 $value = $v;
 }
 return $value;
}

Any possible improvements? :)

• mickmackusa: What if the deep value that you want is a zero, but your script returns null? If you are going to call empty() that should happen before null coalescing.
• mickmackusa: Your break seems like it is part of a protective measure. Would you prefer instead to throw an exception because the path to the desired element suffered a breakage? How do you differentiate between a truly found null and a fallback null?
• Luca Reghellin: @mickmackusa the break is there because if the value is not the one expected or is undefined/null/empty string, I want a null value. If $v == 0, it will return 0, not null.

Answer 1

I recommend avoiding declaring single-use variables. I also recommend throwing an exception when a broken path is passed into your function. Better variable naming will help others to instantly understand your code.

Code: (Demo)

function get_array_deep_value(array $array, array $levelKeys) {
 foreach ($levelKeys as $index => $key) {
 if (!key_exists($key, $array)) {
 throw new Exception("key $key not found at level index $index");
 }
 $array = $array[$key];
 }
 return $array;
}
$myArray = [
 'one' => [
 'two' => [
 'three' => [
 4
 ]
 ]
 ]
];
$pathArrays = [
 ['one', 'two', 'three'],
 ['one', 'two'],
 ['one'],
 ['two']
];
foreach ($pathArrays as $pathArray) {
 try {
 var_export(get_array_deep_value($myArray, $pathArray));
 } catch (Exception $e) {
 echo $e->getMessage();
 }
 echo "\n---\n";
}

• Luca Reghellin: Hey, key_esists... Wow... Elegant... :) Thank you! But will the exception also break the loop?
• mickmackusa: No, it is caught. Add another valid path to test this.
• Luca Reghellin: ' Add another valid path to test this': what do you mean? Anyway, I need always null when the value is not found/valid, since that value will be written on a database field.
• mickmackusa: You can assign the fallback variable in the catch body 3v4l.org/rvhX9 or just return null without throwing an exception, but it will be a more professional approach to differentiate truly extracted values from fallback values.
• mickmackusa: Fair enough, then that logical requirement should be expressed in your question and in your project's code.