Wildcard array loop in PHP

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().

you have to iterate over the whole array and check the key for a matching pattern — Vlad Balmos
– Vlad Balmos, Commented Oct 3, 2012 at 12:56

Baba · Accepted Answer · 2012-10-03 13:19:52Z

7

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)

edited Oct 3, 2012 at 13:19

answered Oct 3, 2012 at 12:56

Baba

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3 Comments

BenM Over a year ago

Thanks for your help. I'd originally thought about this, but wondered if there was a more efficient way than looping through the entire array. It'd appear not!

Baba Over a year ago

Please see updated code with the use of === instead because == can return 0 when a boolean response is received

hounded Over a year ago

a speed test on each method could be helpful ;)

Teena Thomas · Accepted Answer · 2012-10-03 13:29:37Z

3

 foreach( $arr as $k => $v ) { //iterate the array
  if( strpos($k, 'default_') !== FALSE  ) //search if the key contains 'default_' 
   $default_values[] = $v;   // if so, store the values for the 'default_' keys   
 }

edited Oct 3, 2012 at 13:29

answered Oct 3, 2012 at 12:55

Teena Thomas

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2 Comments

Baba Over a year ago

Ran your code out of curiosity and it does not work see codepad.viper-7.com/9DjEKz . It returns My App which should not be in the list

Teena Thomas Over a year ago

Edited the conditional check.

Marcin Orlowski · Accepted Answer · 2012-10-03 12:57:05Z

2

Just iterate over your array

Foreach( $inputArray AS $key=>$val ) {
  // check if key is the one we need
  if( ... ) {
     // it is - deal with it
  }
}

depending of the keys you use if() can be simple substr() or regexp matching.

edited Oct 3, 2012 at 12:57

answered Oct 3, 2012 at 12:56

Marcin Orlowski

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Comments

Sven · Accepted Answer · 2012-10-03 13:07:11Z

2

You can use a FilterIterator for this.

Its essetially the same as looping over the whole array, because that's the only way really, but it strips you from doing this in your productive loop, thus generating less noise.

Here's how:

class Default_FilterIterator extends FilterIterator
{
    public function accept()
    {
      if (strpos($this->key(), 'default') === 0) {
        return true;
      }
      return false;
    }
}


$yourArray = array('default_stuff' => 'foo', 'otherstuff' => 'bar');

$filterdArray = new Default_FilterIterator(new ArrayIterator($yourArray));

foreach ($filteredArray as $key => $value) {
  //deal only with default values here
}

answered Oct 3, 2012 at 13:07

Sven

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Comments

Hank · Accepted Answer · 2012-10-03 13:03:09Z

1

   foreach ($your_array as $key => $value) {
     // check if the $key starst with 'default_'
     if (substr($key, 0, 8) == "default_") {
      //do your thing...
      echo "<input type='text' value='" . $value . "'>";
     }
   }

answered Oct 3, 2012 at 13:03

Hank

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