helpe to convert from java to php [closed]

I have written a java code and I need help writing it in PHP because I do not have enough experience with PHP

public static String mo31385a(String str, String str2, String str3) {
    int length = str.length();
    char[] cArr = new char[length];
    for (int i = 0; i < length; i++) {
        char charAt = str.charAt(i);
        int indexOf = str2.indexOf(charAt);
        if (indexOf < 0) {
            cArr[i] = charAt;
        } else {
            cArr[i] = str3.charAt(indexOf);
        }
    }
    return new String(cArr);
}

i want thes function by php plz

Answer

Here:

function mo31385a($str, $str2, $str3)
    {
        $cArr = array();
        for ($i = 0; $i < strlen($str); $i++)
        {
            $charAt = $str[$i];
            $indexOf = strpos($str2,$charAt);
            if (!$indexOf)
            {
                $cArr[] = $charAt;
                continue;
            }
            $cArr[] = $str3[$indexOf];  
        }
        return implode("",$cArr);
    }