Converting text with link to hyperlink in PHP

<?php

// string with URL's need to be changed to html format adding the the <a> tag

$str1 = "my name is kishore and my web page is http://www.kisaso.com all are welcom 

http://kish.in isPR checker which also display the pagerank of the current page 

with a small image. I am testing http://this.com plugin on my blog and need 

to do some work o";

changeToUrl($str1);

function changeToUrl($str) {

    $flag=true;

    // storing the original text

    $tempStr = $str;

    for($i=0 ; $flag==true; $i++) {

        //Getting the first http position, I checking if any text begins with http, you can 

//modify this according to your need

        $httpos = strpos($tempStr, 'http');

        //checking if any more http available in the text

        if( $httpos === false) $flag=false;

        // Removing the text before the http position

        $afterurl = substr($tempStr, $httpos);

        // Getting the space postion after the url which means the end of the URL

        $gapos = strpos($afterurl, " ");

        // Getting the URL text for which we need to replace with the <a> tag

        $finalurl = substr($afterurl, 0, $gapos);

        // Getting the length of the URL

        $lengthOfUrl = strlen($finalurl);

        //Getting the text removing the URL that is to scan for the next URL    

        $tempStr = substr($afterurl,$lengthOfUrl);

        // This will replace the URL adding the <a> tag

        $replace = '<a href ='.$finalurl.'>'.$finalurl.'</a>';

        // replacing the URL with <a> tag

        $includelink = str_replace($finalurl, $replace, $str);

        // Saving the new string after replacing the URL with <a> tag and goes to the next URL

        $str=$includelink;

    }

    echo $includelink;

}

?>