Question

I have an array which contains a great deal of data, which has been generated from a JSON file. Most of the data is used to populateinput elements, but some of the keys contain hidden, default values to be used for calculations later.

The array looks something like this:

[name] => 'My App'
[default_E17] => 0.009
[default_H17] => 0.0236
[default_K17] => 50
[default_P17] => 0.0118
[default_E19] => 0.03

I want to loop over all default_* keys, and output them using HTML. Essentially, I want a foreach loop, but only for the keys whose format matches default_*. Does anyone know if this is possible?

Please note that the values in the array before [default_*] keys is variable length, so I cannot easily use an array_splice().

Answer 1

You use strpos($key, "default_") === 0 to show that it start with default_ and its not in the middle or end

$array = array();
$array['name'] = 'My App';
$array['default_E17'] = "0.009";
$array['default_H17'] = "0.0236";
$array['default_K17'] = "50";
$array['default_P17'] = "0.0118";
$array['default_E19'] = "0.03";
$array['E19_default_test'] = "1.03";


echo "<pre>";

* You can use foreach *

$list = array();
foreach ( $array as $key => $value ) {
    if (strpos($key, "default_") === 0) {
        $list[$key] = $value;
    }
}

var_dump($list);

You can also use array_flip with array_filter

$array = array_flip(array_filter(array_flip($array),function($var) { return (strpos($var, "default_") === 0);}));
var_dump($array);

You can also use FilterIterator

class RemoveDefaultIterator extends FilterIterator {
    public function accept() {
        return (strpos($this->key(), "default_") === 0);
    }
}

$list = new RemoveDefaultIterator(new ArrayIterator($array));
var_dump(iterator_to_array($list));

They would all Output

array
  'default_E17' => string '0.009' (length=5)
  'default_H17' => string '0.0236' (length=6)
  'default_K17' => string '50' (length=2)
  'default_P17' => string '0.0118' (length=6)
  'default_E19' => string '0.03' (length=4)