$re = '/url\(((?:\/[^\/()]+?)+?\.(gif|png|jpg|jpeg|svg|woff|eot|ttf))[^)]*\)/mi';
$str = 'url(/var/www/synergicNetwork/app/webroot/img/mosaico.png) no-repeat center center fixed; color:#fff; background-size:cover; url(/var/www/synergicNetwork/app/webroot/img/mosaico.png) no-repeat center center fixed; color:#fff; background-size:cover;
url(/ghfdgh/glyphicons-halflings-regular.eot?#iefix) format(\'embedded-opentype\'),url(/fonts/glyphicons-halflings-regular.woff)';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php