Retain elements in array if associative key starts with specific substring [duplicate]

If I have array like:

array [
       y => 35
       x => 51
       z => 35
       c_3 => 4
       c_1 => 54
       c_6 => 53
       c_9 => 52
] 

I want to get array of:

array [c_3=>4, c_1=>54, c_6=>53, c_9=>52]

How can I filter out the elements which do not have keys starting with c_?

Solution 1:

Try this :

$filtred = array();

foreach($yourArray as $key => $value)
  if(preg_match('/c_\d/',$key))
    $filtred[] = $value;

print_r($filtred);

Solution 2:

Try This

 //your array
    $arr1 = array (
           "y" => 35,
           "x" => 51,
           "z" => 35,
           "c_3" => 4,
           "c_1" => 54,
           "c_6" => 53,
           "c_9" => 52
    );
// Array with keys you want
    $arr2 =  array (
           "c_3" => '',
           "c_1" => '',
           "c_6" => '',
           "c_9" => ''
    );
//use array_intersect_key to find the common  ;)
    print_r(array_intersect_key($arr1,$arr2));

Solution 3:

Check this solution with array_filter()

 $arr = [
   'y' => 35,
   'x' => 51,
   'z' => 35,
   'c_3' => 4,
   'c_1' => 54,
   'c_6' => 53,
   'c_9' => 52,
 ];

 $filtered = array_filter($arr, function($v) use($arr){
   return preg_match('#c_\d#', array_search($v, $arr));
 });

Solution below will work in PHP >= 5.6.0

 $filtered = array_filter($arr, function($k){
   return preg_match('#c_\d#', $k);
 }, ARRAY_FILTER_USE_KEY);

Both solutions work I've checked them.

Solution 4:

You can try using array_filter().

There are some interesting examples on the php documentation page. One of them covers filtering array keys.