php正则替换

ere2w

$string = 'April 15, 2003';
$pattern = '/(\w+) (\d+), (\d+)/i';
$replacement = '${1}1,\3';
//$replacement = '${1}1,$3';
//$replacement = '${1}1,{3}';

echo preg_replace($pattern, $replacement, $string);
echo '<br/>';
//-----------------------------

$string = 'The quick brown fox jumped over the lazy dog.';
$patterns = array();
$patterns[0] = '/quick/';
$patterns[1] = '/brown/';
$patterns[2] = '/fox/';
$replacements = array();
$replacements[2] = 'bear';
$replacements[1] = 'black';
$replacements[0] = 'slow';
echo preg_replace($patterns, $replacements, $string);

echo '<br/>';
//---------------------------------
    //$d = $db->select('select * from <{:task}> limit 2');
        self::$_sql = preg_replace('/<{:\s*(.*?)\s*}>/', $this->_prefix . '\1', $sql);
        $this->_res = mysql_query(self::$_sql, $this->_db);

//---------------------------------
    if (preg_match('/^p-(\d+)$/', $segment3, $m)) {
            $page = intval($m[1]);
        }
        else if (preg_match('/^\d+$/', $segment3)) {
            $task_type = intval($segment3);
            if (preg_match('/^p-(\d+)$/', $setment4, $m2)) {
                $page = intval($m2[1]);
            }   
        }