Hiea

<?php
    $array = [2,3,4,5,3,7,2,2];
    
    $buffer = [];
    
    foreach ($array as $k => $v) {
        $found = false;
        
        foreach ($buffer as $sk => $sv) {
            if ($v == $sv) {
                $found = true;
            }
        }
        
        if (!$found) {
            $buffer[] = $v;
        }
    }
    
    foreach ($buffer as $k => $v) {
        echo $v;
    }
?>