StringsInPHP - //Problem 6. Combine List of Letters

//Problem 6.    Combine List of Letters
//Write a script  that reads two array of letters l1 and l2 and combines them: appends all letters c from l2 to the end of l1, but only //when c does not appear in l1. Print the obtained combined list. All lists are given as sequence of letters separated by a single space, //each at a separate line. Use ArrayList<Character> of chars to keep the input and output lists

<?php
//$str1=array('h', 'e', 'l', 'l', 'o');
//$str2=array('l','o','w');
$str1=array('a', 'b', 'c', 'd');
$str2=array('x','y','z');
for($i=0;$i<=count($str2)+1;$i++){
    for($j=0;$j<=count($str1)+1;$j++){
        if ($str1[$j]==$str2[$i]) {
            $flag=0;
            break;
        }
        elseif($str1[$j]!=$str2[$i]){
            $flag++;
        }
    }
    if($flag!=0){
        $str1[]=$str2[$i];
    }
    $flag=0;
}
echo '<pre>' . print_r($str1, true) . '</pre>';
?>