php 正则替换掉网页中所有超链接 过滤网页中所有Url

<?php
$content = file_get_contents('test.html');
$url = 'http://www.111cn.net';  //要换成的新网址
$preg = '/[s]href=("|')[S]*("|')/i';
$replace = ' href="' . $url . '"';
$content = preg_replace($preg, $replace, $content);  //正则替换
create_log('newhtml', $content);  //生成新文件
?>

function create_log($filename, $text) {
       if ( strtolower(substr($filename, -4)) != 'html' ){
              $filename .= '.html';
       }
       $filename = dirname ( __FILE__ ) . '/' . $filename;
       if (!file_exists ( $filename )) {
              exec( 'touch '. $filename);
              exec( 'chmod 777 '. $filename);
       }
       $handle = fopen ( $filename, "w+b" );
       $text .= "rn";
       fwrite($handle, $text);
       fclose ( $handle );
}

$url ='http://www.111cn.net';
$body=@file_get_contents($url);
preg_match_all('/href=['"]?([^'"]*)['"]?>(.*)/i',$body,$b);
$nums = array();
foreach($b[1] as $u){
  if(in_array($u,$nums)){
  continue;
  }
  $nums[]=$u;
  $title=strip_tags($u);
  echo $title."</br>";
}

$array = array(
    array('class' => 'a', 'value' => 3),
    array('class' => 'a', 'value' => 4),
    array('class' => 'b', 'value' => 5),
    array('class' => 'b', 'value' => 6)
)

array_avg($array, 'class');//返回二维数组
array_avg($array);//返回一维数组
// 计算平均值    返回一维数组
// 参数$avgby 按照指定字段算平均值  返回二维数组
private function array_avg($array, $avgby = NULL) {
    $array_avg = array ();
    $number = count ( $array );
    foreach ( $array as $key => $value ) {
        if ($avgby) {
            $avg_key = $value[$avgby];
            $array_avg[$avg_key]['count'] ++;
            foreach ( $value as $k => $v ) {
                $array_avg[$avg_key][$k] += $v;
            }
        } else {
            foreach ( $value as $k => $v ) {
                $array_avg[$k] += $v;
            }
        }
    }
    $array = array ();
    foreach ( $array_avg as $key => $value ) {
        if ($avgby) {
            foreach ( $value as $k => $v ) {
                $array[$key][$k] = $v / $value['count'];
            }
        } else {
            $array[$key] = $value / $number;
        }
    }
    return $array;
}

/**
  * 当前请求是否ajax请求
  *
  * @access public
  * @return bool
  */
 function isAjax()
 {
     return isset($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'XMLHttpRequest';
 }

switch ($_SERVER['HTTP_ACCEPT']){ 
    case 'application/json, text/javascript, */*': 
        //  JSON 格式 
        break; 
    case 'text/javascript, application/javascript, */*': 
        // javascript 或 JSONP 格式 
        break; 
    case 'text/html, */*': 
        //  HTML 格式 
        break; 
    case 'application/xml, text/xml, */*': 
        //  XML 格式 
        break; 
}

header("refresh:3;url=http://www.111cn.net");//限时跳转
header('location:http://www.111cn.net');//立即跳转

<meta http-equiv="refresh" content="3; url=http://www.111cn.net">

<script type='text/javascript'>
 // 立即跳转
 window.location.href = 'http://www.111cn.net';
 // 限时跳转
 setTimeout(function(){
  // 3秒后跳转
  window.location.href = 'http://www.111cn.net';
 },3000);
</script>

function getFirstCharter($str) {
    if (empty($str)) {return '';}
    $fchar = ord($str{0});
    if ($fchar>=ord('A') && $fchar<=ord('z')) return strtoupper($str{0});
    $s1 = iconv('UTF-8', 'gb2312', $str);
    $s2 = iconv('gb2312', 'UTF-8', $s1);
    $s = $s2 == $str ? $s1 : $str;
    $asc = ord($s{0})*256 + ord($s{1}) - 65536;
    if ($asc>=-20319 && $asc<=-20284) return 'A';
    if ($asc>=-20283 && $asc<=-19776) return 'B';
    if ($asc>=-19775 && $asc<=-19219) return 'C';
    if ($asc>=-19218 && $asc<=-18711) return 'D';
    if ($asc>=-18710 && $asc<=-18527) return 'E';
    if ($asc>=-18526 && $asc<=-18240) return 'F';
    if ($asc>=-18239 && $asc<=-17923) return 'G';
    if ($asc>=-17922 && $asc<=-17418) return 'H';
    if ($asc>=-17417 && $asc<=-16475) return 'J';
    if ($asc>=-16474 && $asc<=-16213) return 'K';
    if ($asc>=-16212 && $asc<=-15641) return 'L';
    if ($asc>=-15640 && $asc<=-15166) return 'M';
    if ($asc>=-15165 && $asc<=-14923) return 'N';
    if ($asc>=-14922 && $asc<=-14915) return 'O';
    if ($asc>=-14914 && $asc<=-14631) return 'P';
    if ($asc>=-14630 && $asc<=-14150) return 'Q';
    if ($asc>=-14149 && $asc<=-14091) return 'R';
    if ($asc>=-14090 && $asc<=-13319) return 'S';
    if ($asc>=-13318 && $asc<=-12839) return 'T';
    if ($asc>=-12838 && $asc<=-12557) return 'W';
    if ($asc>=-12556 && $asc<=-11848) return 'X';
    if ($asc>=-11847 && $asc<=-11056) return 'Y';
    if ($asc>=-11055 && $asc<=-10247) return 'Z';
    return null;
} 

例如：
 

echo getFirstCharter("程序员3aj.cn"); // 结果将输出：C