$text = '数组aabbccdd';
$text_filter = '';
$filter = array();
$len = mb_strlen($text, 'utf-8');
for ($i = 0; $i<$len; $i++) {
$char = mb_substr($text, $i, 1, 'utf-8');
if (!isset($filter[$char])) {
$text_filter .= $char;
$filter[$char] = $char;
}
}
echo $text_filter;

$string= '数组aabbccdd';
function str_split_utf8($str) {
$split=1;
$array = array();
for ( $i=0; $i < strlen( $str ); ){
$value = ord($str[$i]);
if($value > 127){
if($value >= 192 && $value <= 223)
$split=2;
elseif($value >= 224 && $value <= 239)
$split=3;
elseif($value >= 240 && $value <= 247)
$split=4;
}else{
$split=1;
}
$key = NULL;
for ( $j = 0; $j < $split; $j++, $i++ ) {
$key .= $str[$i];
}
array_push( $array, $key );
}
return $array;
}
print_r(array_unique(str_split_utf8($string)));