PHP Functions for converting string to ASCII

convertToAscii.php

<?php

/**
 * Normalize non-ASCII characters to ASCII counterparts where possible.
 *
 * @param string $str
 * @return string
 */
function squashCharacters($str)
{
    static $normalizeChars = null;
    if ($normalizeChars === null) {
        $normalizeChars = array(
            'À'=>'A', 'Á'=>'A', 'Â'=>'A', 'Ã'=>'A', 'Ä'=>'A', 'Å'=>'A', 'Æ'=>'Ae',
            'Ç'=>'C',
            'È'=>'E', 'É'=>'E', 'Ê'=>'E', 'Ë'=>'E',
            'Ì'=>'I', 'Í'=>'I', 'Î'=>'I', 'Ï'=>'I',
            'Ð'=>'Dj',
            'Ñ'=>'N',
            'Ò'=>'O', 'Ó'=>'O', 'Ô'=>'O', 'Õ'=>'O', 'Ö'=>'O', 'Ø'=>'O',
            'Ù'=>'U', 'Ú'=>'U', 'Û'=>'U', 'Ü'=>'U',
            'Ý'=>'Y',
            'Þ'=>'B',
            'ß'=>'Ss',
            'à'=>'a', 'á'=>'a', 'â'=>'a', 'ã'=>'a', 'ä'=>'a', 'å'=>'a', 'æ'=>'ae',
            'ç'=>'c', 'è'=>'e', 'é'=>'e', 'ê'=>'e', 'ë'=>'e',
            'ì'=>'i', 'í'=>'i', 'î'=>'i', 'ï'=>'i',
            'ð'=>'o', 'ñ'=>'n', 'ò'=>'o', 'ó'=>'o', 'ô'=>'o', 'õ'=>'o', 'ö'=>'o', 'ø'=>'o',
            'ù'=>'u', 'ú'=>'u', 'û'=>'u',
            'ý'=>'y',
            'þ'=>'b',
            'ÿ'=>'y',
            'Š'=>'S', 'š'=>'s', 'ś' => 's',
            'Ž'=>'Z', 'ž'=>'z',
            'ƒ'=>'f'
        );
    }
    return strtr($str, $normalizeChars);
}

/**
 * Convert all fields in $item to ASCII.
 *
 * Do this by first normalizing the characters (á -> a, ñ -> n, etc.). If any
 * non-ASCII characters remain, replace with a default value.
 *
 * @param array|object $item Array or object containing fields to convert
 * @param array|object $template Contains template fields
 * @param string $default Value to use when field not present in $template
 * @param array $ignore Optional list of fields to ignore.
 */
function convertFieldsToAscii(&$item, $template=null, $default='', array $ignore=null)
{
    foreach ($item as $field => &$value) {

        // Skip fields in the $ignore array.
        if ($ignore && in_array($field, $ignore)) {
            continue;
        }

        // Normalize non-ASCII characters with ASCII counterparts.
        $value = squashCharacters($value);

        // Replace fields that contain non-ASCII characters with a default.
        if (mb_convert_encoding($value, 'ascii') !== $value) {
            // If template is provided, use the template field, if set.
            if ($template) {
                if (is_object($template) && isset($template->{$field})) {
                    $value = $template->{$field};
                } elseif (is_array($template) && isset($template[$field])) {
                    $value = $template[$field];
                } else {
                    $value = $default;
                }
            } else {
                $value = $default;
            }
        }
    }
}

Thanks. I'd like to mention that German umlauts are converted to two char sequences:
[ 'ä' => 'ae', 'ö' => 'oe', 'ü' => 'ue', 'Ä' => 'Ae', 'Ö' => 'Oe', 'Ü' => 'Ue'] and also ['ß' => 'sz' ]