foreach doesn't print altered array properly

Question

I am trying to print an array using foreach and while printing, if a certain $key comes up, I want to make changes to the array. Problem is, even though the array gets changed, the changes do not get printed.

In the example below, you will find:

• function I use to change the array;
• an array first printed with no changed;
• then echo print-out in with changes during the process - all using foreach;

• another print-out of the same table, but this time with changes.

  <?php
  
  function insert_before_key($array, $key, $data = NULL){
      if (($offset = array_search($key, array_keys($array))) === false){
          $offset = count($array); 
      }
      return array_merge(array_slice($array, 0, $offset), (array) $data, array_slice($array, $offset));
  }
  
  $array = array(
      "no_color"  =>  "blank",
      "color1"    =>  "red",
      "color2"    =>  "green",
      "color3"    =>  "blue",
      );
  
  echo "<pre>";
  print_r($array);
  echo "</pre>";
  
  foreach ($array as $key => $value) {
      echo $key . ": " . $value . "<br />";
      if ($key === "color1"){
          $array = insert_before_key($array, "color2", array("color1.5" => "yellow"));
      }
  }
  
  echo "<pre>";
  print_r($array);
  echo "</pre>";
  
  echo "<br />";
  
  ?>
  

Note that the new $key is to jump in AFTER current $key, so I would expect it to come up. Any idea why this happens ?

EDIT:

Played a bit more with foreach and I think it must be caching the keys or something...

    <?php
    $test_array = array(0,1,2,3,4,5,6,7,8,9);

    foreach ($test_array as $key => $value) {
        if ($key === 5){$test_array[7] = $test_array[7]+1;}
        echo $key . ": " . $value . "<br />";
    }

    print_r($test_array);
    ?>

The above will display UNCHANGED echo, but CHANGED print_r.

Answer 1

I'd keep it simple. Something tells me however that you're fixing effects of a problem here and not its source.

$array = array(
    "no_color"  =>  "blank",
    "color1"    =>  "red",
    "color2"    =>  "green",
    "color3"    =>  "blue",
);

$temp_array = array();

foreach ($array as $key => $value) {
    $temp_array[$key] = $value;
    echo $key . ": " . $value . "<br />";
    if ($key == 'color1') {
        $key_add = 'color1.5';
        $value_add = 'yellow';
        $temp_array[$key_add] = $value_add;
        echo $key_add . ": " . $value_add . "<br />";
    }
}

$array = $temp_array;

Answer 2

From the manual: "As foreach relies on the internal array pointer, changing it within the loop may lead to unexpected behavior." http://php.net/manual/en/control-structures.foreach.php

You shouldn't modify an array you're looping over.

Answer 3

So during iteration you are trying to change the value of the item being iterated

foreach($array ...)
{
    change $array
}

Use a copy of $array inside the iteration

 $array2 = $array
 foreach($array ...)
{
    change $array2
}