php 防注入與字元反過濾代碼

//==防注入自動過濾[啟用後程式效率低]==========================================================================================
/*
function inject_checks($sql_str){return eregi('select|insert|update|delete|'|/*|*|../|./|union|into|load_file|outfile', $sql_str);}
foreach ($_REQUEST as $value){if (inject_checks($value)){echo "<script language=javascript>alert('你提交的資料非法，請檢查後重新提交！');</script>";exit;}}
*/
//==防注[inject_check($sql_str)]==========================================================================================
function inject_check($sql_str){
if (eregi('select|insert|update|delete|union|into|load_file|outfile', $sql_str)){echo "<script language=javascript>alert('你提交的資料非法，請檢查後重新提交！');</script>";exit;}
return $sql_str;
}
//==字元過濾[safe_convert($string)]==============================================================================
function safe_convert($string){ //Words Filter
if(get_magic_quotes_gpc()){ //逸出字元 加上反斜線
        $string=htmlspecialchars($string, ENT_QUOTES); //將特殊字元轉成HTML字串格式如 "&"轉成"&amp;"
        $string=str_replace("<","&lt;",$string); //替換
        $string=str_replace(">","&gt;",$string); //替換
        $string=str_replace("\", '&#92;', $string); //替換  
    } else {
        $string=addslashes($string); //逸出字元 加上反斜線 //$string=stripslashes($string); //去掉反斜線
        $string=str_replace("\\", '&#92;', $string);
    }
    //$string=str_replace("r","<br/>",$string); //換行
    //$string=str_replace("n","",$string); //空格
    $string=str_replace("t","&nbsp;&nbsp;",$string); //空格
    $string=str_replace("  "," &nbsp;",$string); //空格
    //$string=str_replace('|', '&#124;', $string); //替換 同分類系統有衝突
    $string=str_replace("&amp;#96;","&#96;",$string); //替換
    $string=str_replace("&amp;#92;","&#92;",$string); //替換
    return $string;
}
//==字元反過濾[unsafe_convert($string)]==============================================================================
function unsafe_convert($string){ //Words Filter
    $string=str_replace("&#92;&quot;","&quot;",$string); //替換
    return $string;
}

//==字元過濾[filter($string)]============================================================================================
function filter($string){ //Words Filter
include("Filter.php");//詞彙過濾列表
foreach($badwords as $badword){
if(stristr($string,$badword)==true){echo "<script language=javascript>alert('警告：你提交的內容含有敏感字眼，請更換內容。');</script>";exit;}
}
return $string;
}