php查询超过256长度字符串，数据被截断的问题

//test.php

function odbc_php_exe( ){

    print("star odbc php test\n");

    //$user="zabbix";

    //$password="123456";

    #$conn=odbc_connect("Driver={MySQL8.0};Server=192.168.7.134;Database= zabbix;", $user, $password);

    //$dsn="Driver={YashanDB};Server=192.168.24.49;Database=yashandb;port=4688;";

    $dsn="Yashandb";

    $user="sys";

    $password="yasdb_123";

    $conn=odbc_connect($dsn, $user, $password);

    //$conn=odbc_connect($dsn,,'123456');

    if (!$conn){

        exit("连接失败: " . $conn);

    }

    $sql = "select c1 ,c2 from test062";

    $rs=odbc_exec($conn,$sql);

    if (!$rs){

        exit("SQL 语句错误");

    }

    print("result:\n");

    while (odbc_fetch_row($rs)){

        $compname=odbc_result($rs,"c1");

        $conname=odbc_result($rs,"c2");

        echo "c1:$compname \n";

        echo "c2:$conname\n";

    }

    odbc_close($conn);

    echo "end\n";

}

function pdo_exe( ){

    try{

      $dsn="odbc:yashandb";

      //$dsn="odbc:MySQLCN";

      $pdo=new PDO($dsn);

      print("conn success\n");

      // 使用pdo->query() 预处理并执行sql语句,以 PDOStatement 对象形式返回结果集,

      // 如果数据不存在则返回false

      $sql = "select c1 ,c2 from test062";

      $rs = $pdo->query($sql);

      // 以关联数组的方式将结果集返回

      $all= $rs->fetchAll(PDO::FETCH_ASSOC);

      print_r($all);

    }catch(PDOException $e){

        die("fail:".$e->getMessage()."\n");

    }

}

//pdo_exe();

odbc_php_exe();

?>