substr return empty string
<p>i have problem with $length of substr function</p>

<p>my CODE</p>

<pre><code>$string='I love stackoverflow.com';
function arabicSubStr($value,$start,$length=false){
    return mb_substr($value,$start,$length,'UTF-8');
}

echo arabicSubStr($string,7);//outputs nothing
echo substr($string,7);//outputs stackoverflow.com
</code></pre>

<p>The reason of the problem is:</p>

<blockquote>
  <p>If length is given and is 0, FALSE or NULL an empty string will be returned. </p>
</blockquote>

<p>So, How i can fix the problem?</p>

<p>i won't use <code>strlen($string)</code></p>

<h1>EDITE</h1>

<p>I know the reason is because i've defined $length as false</p>

<p>And i am  here to know what should i put in $length parameter to avoid this error?</p>

<p>i am trying to put -1 it's returns //stackoverflow.co</p>
