how to make a string lowercase without changing url

Question

I'm using mb_strtolower to make a string lowercase, but sometimes text contains urls with upper case. And when I use mb_strtolower, of course the urls changing and not working.

How can I convert string to lower without changin urls?

Answer 1

Here you go, iterative, but as fine as possible.

    function strtolower_sensitive ( $input ) {
            $regexp = "#((http|https|ftp)://(\S*?\.\S*?))(\s|\;|\)|\]|\[|\{|\}|,|\"|'|:|\<|$|\.\s)#ie";
            if(preg_match_all($regexp, $input, $matches, PREG_SET_ORDER)) {
                    for( $i=0, $hist=array(); $i<=count($matches); ++$i ) {
                            str_replace( $u=$matches[$i][0], $n="sxxx".$i+1, $input ); $hist[]=array($u,$n);
                    }
                    $input = strtolower($input);
                    foreach ( $hist as $h ) {
                            str_replace ( $h[1], $h[0], $input );
                    }
            }
            return $input;
    }

$input is your string, $output will be your answer. =)

Answer 2

Since you have not posted your string, this can be only generally answered.

Whenever you use a function on a string to make it lower-case, the whole string will be made lower-case. String functions are aware of strings only, they are not aware of the contents written within these strings specifically.

In your scenario you do not want to lowercase the whole string I assume. You want to lowercase only parts of that string, other parts, the URLs, should not be changed in their case.

To do so, you must first parse your string into these two different parts, let's call them text and URLs. Then you need to apply the lowercase function only on the parts of type text. After that you need to combine all parts together again in their original order.

If the content of the string is semantically simple, you can split the string at spaces. Then you can check each part, if it begins with http:// or https:// (is_url()?) and if not, perform the lowercase operation:

$text = 'your content http://link.me/now! might differ';
$fragments = explode(' ', $text);
foreach($fragments as &$fragment) {
    if (is_not_url($fragment)) 
        $fragment = strtolower($fragment) // or mb_strtolower
        ;
}
unset($fragment); // remove reference
$lowercase = implode(' ', $fragments);

To have this code to work, you need to define the is_not_url() function. Additionally, the original text must contain contents that allows to work on rudimentary parsing it based on the space separator.

Hopefully this example help you getting along with coding and understanding your problem.