PHP如何实现图片添加文字，生成新图片

/*
**生成证书图片
**$BlockHash 区块hash
**
*/
public function createNewPic($mer_id,$mer_name,$BlockHash,$TxID){
    //背景图片
    $path_1 = 'img/background_code.png';
    //照片
    $path_2= 'img/1.png';
    //建立图片对象
    $image_1 = imagecreatefrompng($path_1);
    $image_2 = imagecreatefrompng($path_2);
    //合成图片
    imagecopymerge($image_1, $image_2, 0, 0, 10, 10, imagesx($image_2), imagesy($image_2), 100);
    //这是要插入到图片的文字
    $data=date('ymd',time());
    $pad=str_pad(1,4,"0",STR_PAD_LEFT);
    $str=mt_rand(10000000,99999999);
    $number=$data.$pad.$subtle.$str; 
    $prove="兹证明：\n\n美嘉兔科技有限公司，产品符合溯源规范，认证内容如下：\n特授权期产品在元一众享溯源商城出售";  
    $prove="兹证明：";  
    $mer_name = "中国溯源旗舰店";
    $merName = $mer_name."，产品符合溯源规范，\n认证内容如下：\n特授权其产品在元一众享溯源商城出售!"; 
    $hash = "930faf66cc24e7a5af56fcdee7c9b726c5869cd763ba5166a22de5f34c3570d5";
    $hash = wordwrap($hash,45,"\n",TRUE);
    $authorization_time = date('Y/m/d',time());
    $valid_time = date("Y/m/d",strtotime("+1years",strtotime(date('Y/m/d',time()))));
    //设置文字颜色
    $black = imagecolorallocate($image_1, 0, 0, 0 );
    $blue = imagecolorallocate($image_1, 27,142,187);
    //写的文字用到的字体
    $font = 'img/msyh.ttf';
    $font2= 'img/msyhbd.ttf';

    //在图片里插入文字$black
    imagettftext($image_1, 20, 0, 290, 340, $black,$font, "证书编号：".$number);
    imagettftext($image_1, 20, 0, 150, 450, $black,$font, $prove);
    imagettftext($image_1, 20, 0, 200, 500, $black,$font, $merName);
    imagettftext($image_1, 20, 0, 140, 730, $blue,$font, "交易哈希：\n".$hash);
    imagettftext($image_1, 20, 0, 570, 1050, $black,$font, "授权时间：".$authorization_time);
    imagettftext($image_1, 20, 0, 570, 1100, $black,$font, "有效期至：".$valid_time);

    //这是合成后的图片保存的路径
    $upload_dir = "pic/";
    //文件名
    $filename="YY";
    $data=date('ymd',time());
    $pad=str_pad(1,2,"0",STR_PAD_LEFT);
    $str=mt_rand(100000,999999);
    $subtle = microtime()*1000000;
    $jobnumber=$data.$pad.$subtle.$str;
    $picture=$upload_dir.$filename.$jobnumber.'.png';
    imagepng($image_1,$picture);
    $url = 'http://'.$_SERVER['HTTP_HOST'].'/'.$picture;
    return  $url;
}

如果添加的文字过长可使用wordwrap()函数进行设置换行。
例如：

$BlockHash = wordwrap($result['data']['blockhash'],42,"\n",TRUE);