php: Array keys case *insensitive* lookup?

Option 1 – change the way you create the array

You can’t do this without either a linear search or altering the original array. The most efficient approach will be to use strtolower on keys when you insert AND when you lookup values.

 $myArray[strtolower('SOmeKeyNAme')]=7;

 if (isset($myArray[strtolower('SomekeyName')]))
 {

 }

If it’s important to you to preserve the original case of the key, you could store it as a additional value for that key, e.g.

$myArray[strtolower('SOmeKeyNAme')]=array('SOmeKeyNAme', 7);

Option 2 – create a secondary mapping

As you updated the question to suggest this wouldn’t be possible for you, how about you create an array providing a mapping between lowercased and case-sensitive versions?

$keys=array_keys($myArray);
$map=array();
foreach($keys as $key)
{
     $map[strtolower($key)]=$key;
}

Now you can use this to obtain the case-sensitive key from a lowercased one

$test="somekeyname";
if (isset($map[$test]))
{
     $value=$myArray[$map[$test]];
}

This avoids the need to create a full copy of the array with a lower-cased key, which is really the only other way to go about this.

Option 3 – Create a copy of the array

If making a full copy of the array isn’t a concern, then you can use array_change_key_case to create a copy with lower cased keys.

$myCopy=array_change_key_case($myArray, CASE_LOWER);