string to url slug convert in php

Function:
<?php

function create_slug($string, $ext='.html'){
    $replace = '-';  
    $string = strtolower($string);

    //remove query string
    if(preg_match("#^http(s)?://[a-z0-9-_.]+\.[a-z]{2,4}#i",$string)){
        $parsed_url = parse_url($string);
        $string = $parsed_url['host'].' '.$parsed_url['path'];

        //if want to add scheme eg. http, https than uncomment next line
        //$string = $parsed_url['scheme'].' '.$string;
    }

    //replace / and . with white space
    $string = preg_replace("/[\/\.]/", " ", $string);

    $string = preg_replace("/[^a-z0-9_\s-]/", "", $string);

    //remove multiple dashes or whitespaces
    $string = preg_replace("/[\s-]+/", " ", $string);

    //convert whitespaces and underscore to $replace
    $string = preg_replace("/[\s_]/", $replace, $string);

    //limit the slug size
    $string = substr($string, 0, 100);

    //slug is generated
    return ($ext) ? $string : $string;
}  
?>

Use It:
$string = "how to become a php expert?";
$slug = create_slug($string);

//it will return
//how-to-become-a-php-expert