str_replace not replacing correctly - php

Question

I have the following, simple code:
$text = str_replace($f,''.$u.'',$text);
where $f is a URL, like http://google.ca, and $u is the name of the URL (my function names it 'Google').
My problem is, is if I give my function a string like
http://google.ca http://google.ca
it returns
Google" target="_blank">Google</a> Google" target="_blank">Google</a>
Which obviously isn't what I want. I want my function to echo out two separate, clickable links. But str_replace is replacing the first occurrence (it's in a loop to loop through all the found URLs), and that first occurrence has already been replaced.
How can I tell str_replace to ignore that specific one, and move onto the next? The string given is user input, so I can't just give it a static offset or anything with substr, which I have tried.
Thank you!

Answer 1

One way, though it's a bit of a kludge: you can use a temporary marker that (hopefully) won't appear in the string:
$text = str_replace ($f, '' . $u . '',
$text);
That way, the first substitution won't be found again. Then at the end (after you've processed the entire line), simply change the markers back:
$text = str_replace ('XYZZYPLUGH', $f, $text);

Answer 2

Why not pass your function an array of URLs, instead?
function makeLinks(array $urls) {
$links = array();
foreach ($urls as $url) {
list($desc, $href) = $url;
// If $href is based on user input, watch out for "javascript: foo;" and other XSS attacks here.
$links[] = '<a href="' . htmlentities($href) . '" target="_blank">'
. htmlentities($desc)
. '</a>';
}
return $links; // or implode('', $links) if you want a string instead
}
$urls = array(
array('Google', 'http://google.ca'),
array('Google', 'http://google.ca')
);
var_dump(makeLinks($urls));

Answer 3

If i understand your problem correctly, you can just use the function sprintf. I think something like this should work:
function urlize($name, $url)
{
// Make sure the url is formatted ok
if (!filter_var($url, FILTER_VALIDATE_URL))
return '';
$name = htmlspecialchars($name, ENT_QUOTES);
$url = htmlspecialchars($url, ENT_QUOTES);
return sprintf('%s', $url, $name);
}
echo urlize('my name', 'http://www.domain.com');
// my name
I havent test it though.

Answer 4

I suggest you to use preg_replace instead of str_replace here like this code:
$f = 'http://google.ca';
$u = 'Google';
$text='http://google.ca http://google.ca';
$regex = '~(?<!<a href=")' . preg_quote($f) . '~'; // negative lookbehind
$text = preg_replace($regex, ''.$u.'', $text);
echo $text . "\n";
$text = preg_replace($regex, ''.$u.'', $text);
echo $text . "\n";
OUTPUT:
Google Google
Google Google