Problems arising from PHP type casting in ==

While trying to work through the issues I mentioned in the last post I started doing some serious digging and testing. Here is what I have found.

PHP seems to use == for determining equivalance when performing array_search, in_array and switch, while using either === or strcmp when doing array_key_exists.

The result of this is that array_search and in_array will return improper results when used on an array with mixed string and integer values. (Another thing I found, that may or may not be related, is that array keys will be cast from strings to integers when those strings are valid integer values.)

array_search() with mixed types

$one = array (
  'abc',
  'abc1',
  111,
  '111b',
  2,
  '2xyz',
  '123a',
  123
);
$two = $one;
for ($i = 0; $i < count($one); $i++) {
  $xkey = array_search($one[$i], $two);
  if(strcmp(strval($one[$i]), strval($two[$xkey])) != 0) {
    // This should NEVER be reached, but it is, often!
    $eq = 'FALSE';
  } else {
    $eq = 'true';
  }
}

array_search() with all strings

$one = array (
  'abc',
  'abc1',
  '111',
  '111b',
  '2',
  '2xyz',
  '123a',
  '123'
);
$two = $one;
for ($i = 0; $i < count($one); $i++) {
  $xkey = array_search($one[$i], $two);
  if(strcmp(strval($one[$i]), strval($two[$xkey])) != 0) {
    // This should NEVER be reached, and with all strings it isn't.
    $eq = 'FALSE';
  } else {
    $eq = 'true';
  }
}

in_array() and array_key_exists()

$array = array('111'=>'111', '11b'=>'11b', '222b'=>'222b','2x22'=>'2x22');
$keys = array_keys($array);
$searches = array('111b',222,11,'222b',2);
foreach ($searches as $search) {
  $ia = (in_array($search, $array))?'true':'false';
  $ake = (array_key_exists($search, $array))?'true':'false';
  if ($search === '222b') {
    // This is the only place where either should return true
    $iaf = ($ia == 'true')?" class=\"$true\"":" class=\"$false\"";
    $akef = ($ake == 'true')?" class=\"$true\"":" class=\"$false\"";
    $notes = "** Both should be true **";
  } else {
    $iaf = ($ia == 'false')?" class=\"$true\"":" class=\"$false\"";
    $akef = ($ake == 'false')?" class=\"$true\"":" class=\"$false\"";
    $notes = "Both should be false";
  }
}

Notice how the array keys are cast to type int in both the original array and in array_keys.

array(4) {
  [111]=>
  string(3) "111"
  ["11b"]=>
  string(3) "11b"
  ["222b"]=>
  string(4) "222b"
  ["2x22"]=>
  string(4) "2x22"
}

array(4) {
  [0]=>
  int(111)
  [1]=>
  string(3) "11b"
  [2]=>
  string(4) "222b"
  [3]=>
  string(4) "2x22"
}

So, it appears that array_key_exists() uses either or === strcmp() while in_array() uses ==

NOTE: Calling array_key_exists() with a string value ‘111’ will return true for an item with a key of int 111. This is not the same behavior as ===, but is the same behavior as strcmp() which must be what is used internally for array_key_exists().

The difference between the 3 operations is clear:

Another area where this becomes an issue is in switch statements. Take the following, for example:

switch()

$array = array(111,'222b');
foreach($array as $val)
{
  $row = ($row == 'row')?'offset_row':'row';
  $false = ($false == 'false')?'offset_false':'false';
  $true = ($true == 'true')?'offset_true':'true';
  switch($val)
  {
    case '111b': // this displays
      $match = '111b';
      $f = " class=\"$false\"";
      $notes = "Incorrect: should have fallen through to next case";
      break;
    case 111: // never makes it here even tho this is correct
      $match = 111;
      $f = " class=\"$true\"";
      $notes = "** Correct **";
      break;
    case 222: // this displays
      $match = 222;
      $f = " class=\"$false\"";
      $notes = "Incorrect: should have fallen through to next case";
      break;
    case '222b': // never makes it here even tho this is correct
      $match = '222b';
      $f = " class=\"$true\"";
      $notes = "** Correct **";
      break;
    default:
      $match = 'no match';
      $f = " class=\"$false\"";
      $notes = "Incorrect: should have matched";
      break;
  }
}