The preg_replace function seems to dissapear '$' characters, and up to two more numeric characters after it. If the character after the dollar sign is not a number, it works as expected.

$string = 'sum: {token} pesos.';
$number= '$123,456.78';
$number2='$ 123,456.78';
echo  "Wrong: ".preg_replace("/\{token\}/i",$number,$string);
echo  "<br>Right: ".preg_replace("/\{token\}/i",$number2,$string);

My configure line:
'./configure' '--with-apxs' '--with-pgsql' '--without-mysql' '--with-openssl' '--enable-ftp' '--with-gd' '--enable-gd-native-ttf'