//防止SQL注入
function check_sql($str){
  $str = str_replace("'","",$str);	
  $str = str_replace(" or ","",$str);
  $str = str_replace(" and ","",$str);
  $str = str_replace(" select ","",$str);
  $str = str_replace(" update ","",$str);
  $str = str_replace(" delete ","",$str);
  $str = str_replace('"','',$str);	
  return $str;	
}

//检查身份证
function check_idcard($idcard){	
    if(strlen($idcard)!=18){ return false; } //只能是18位    
    $idcard_base = substr($idcard, 0, 17); //取出本体码    
    $verify_code = substr($idcard, 17, 1); //取出校验码    
    $factor = array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2); //加权因子    
    $verify_code_list = array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2'); //校验码对应值 
    //根据前17位计算校验码
    $total = 0;
    for($i=0; $i<17; $i++){
        $total += substr($idcard_base, $i, 1)*$factor[$i];
    }    
    $mod = $total % 11; //取模 
    //比较校验码
    if($verify_code == $verify_code_list[$mod]){
        return true;
    }else{
        return false;
    } 
}

//检查手机号
function check_tel($tel){	
    $search = '/^0?1[3|4|5|6|7|8|9][0-9]\d{8}$/';
    if(preg_match($search, $tel)){
        return true;
    }else{
        return false;
    }
}