PHP case-insensitive in_array function

Question

Is it possible to do case-insensitive comparison when using the in_array function?

So with a source array like this:

$a= array(
 \'one\'         


        

Answer 1

I wrote a simple function to check for a insensitive value in an array the code is below.

function:

function in_array_insensitive($needle, $haystack) {
   $needle = strtolower($needle);
   foreach($haystack as $k => $v) {
      $haystack[$k] = strtolower($v);
   }
   return in_array($needle, $haystack);
}

how to use:

$array = array('one', 'two', 'three', 'four');
var_dump(in_array_insensitive('fOUr', $array));

Answer 2

function in_arrayi($needle, $haystack) {
    return in_array(strtolower($needle), array_map('strtolower', $haystack));
}

From Documentation

Answer 3

The above is correct if we assume that arrays can contain only strings, but arrays can contain other arrays as well. Also in_array() function can accept an array for $needle, so strtolower($needle) is not going to work if $needle is an array and array_map('strtolower', $haystack) is not going to work if $haystack contains other arrays, but will result in "PHP warning: strtolower() expects parameter 1 to be string, array given".

Example:

$needle = array('p', 'H');
$haystack = array(array('p', 'H'), 'U');

So i created a helper class with the releveant methods, to make case-sensitive and case-insensitive in_array() checks. I am also using mb_strtolower() instead of strtolower(), so other encodings can be used. Here's the code:

class StringHelper {

public static function toLower($string, $encoding = 'UTF-8')
{
    return mb_strtolower($string, $encoding);
}

/**
 * Digs into all levels of an array and converts all string values to lowercase
 */
public static function arrayToLower($array)
{
    foreach ($array as &$value) {
        switch (true) {
            case is_string($value):
                $value = self::toLower($value);
                break;
            case is_array($value):
                $value = self::arrayToLower($value);
                break;
        }
    }
    return $array;
}

/**
 * Works like the built-in PHP in_array() function — Checks if a value exists in an array, but
 * gives the option to choose how the comparison is done - case-sensitive or case-insensitive
 */
public static function inArray($needle, $haystack, $case = 'case-sensitive', $strict = false)
{
    switch ($case) {
        default:
        case 'case-sensitive':
        case 'cs':
            return in_array($needle, $haystack, $strict);
            break;
        case 'case-insensitive':
        case 'ci':
            if (is_array($needle)) {
                return in_array(self::arrayToLower($needle), self::arrayToLower($haystack), $strict);
            } else {
                return in_array(self::toLower($needle), self::arrayToLower($haystack), $strict);
            }
            break;
    }
}
}

Answer 4

/**
 * in_array function variant that performs case-insensitive comparison when needle is a string.
 *
 * @param mixed $needle
 * @param array $haystack
 * @param bool $strict
 *
 * @return bool
 */
function in_arrayi($needle, array $haystack, bool $strict = false): bool
{

    if (is_string($needle)) {

        $needle = strtolower($needle);

        foreach ($haystack as $value) {

            if (is_string($value)) {
                if (strtolower($value) === $needle) {
                    return true;
                }
            }

        }

        return false;

    }

    return in_array($needle, $haystack, $strict);

}


/**
 * in_array function variant that performs case-insensitive comparison when needle is a string.
 * Multibyte version.
 *
 * @param mixed $needle
 * @param array $haystack
 * @param bool $strict
 * @param string|null $encoding
 *
 * @return bool
 */
function mb_in_arrayi($needle, array $haystack, bool $strict = false, ?string $encoding = null): bool
{

    if (null === $encoding) {
        $encoding = mb_internal_encoding();
    }

    if (is_string($needle)) {

        $needle = mb_strtolower($needle, $encoding);

        foreach ($haystack as $value) {

            if (is_string($value)) {
                if (mb_strtolower($value, $encoding) === $needle) {
                    return true;
                }
            }

        }

        return false;

    }

    return in_array($needle, $haystack, $strict);

}

Answer 5

• in_array accepts these parameters : in_array(search,array,type)
• if the search parameter is a string and the type parameter is set to TRUE, the search is case-sensitive.
• so in order to make the search ignore the case, it would be enough to use it like this :

$a = array( 'one', 'two', 'three', 'four' );

$b = in_array( 'ONE', $a, false );