CURLOPT_URL codification with PREG_REPLACE value - php

Question

When i get the $url varible by preg_replace feedback it doesn't work but it i specify the $url value with the commented line it works. What's wrong in my code please? Many thanks.
$content = preg_replace('/(plugin_[^ ]+)/', getPlugin('$1'), $content);
function getPlugin($plugin) {
$url = "http://".$_SERVER['HTTP_HOST']."/{$plugin}.php?language=en";
//$url = "http://".$_SERVER['HTTP_HOST']."/plugin_contact.php?language=en";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
$data = curl_exec($ch);
curl_close($ch);
return $data;
}

Answer 1

My solution
if (preg_match("/(plugin_[^ ]+)/", "$content", $match)) {
$content = preg_replace('/(plugin_[^ ]+)/', getPlugin($match[0]), $content);
}

Answer 2

Your original code doesn't work because getPlugin() runs before preg_replace(). It is called with the literal '$1' as argument, there is nobody to replace $1 with something else because preg_replace() is not involved.
I suppose you are refactoring a call to preg_replace() that uses the deprecated e(PREG_REPLACE_EVAL) modifier:
$content = preg_replace('/(plugin_[^ ]+)/e', 'getPlugin("$1")', $content);
In order to remove the /e modifier you can use preg_replace_callback():
$content = preg_replace_callback('/(plugin_[^ ]+)/', 'getPlugin', $content);
function getPlugin(array $matches) {
$plugin = $matches[1];
$url = "http://".$_SERVER['HTTP_HOST']."/{$plugin}.php?language=en";
//$url = "http://".$_SERVER['HTTP_HOST']."/plugin_contact.php?language=en";
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
$data = curl_exec($ch);
curl_close($ch);
return $data;
}