本文借助科大讯飞公式识别 API开放平台，使用PHP构建一个API。

还没有使用讯飞星火的朋友可以参考此文（附机器翻译API源码）

讯飞星火大模型API矩阵

index.php获取待识别的图片，存储到本地调用，识别完成后删除图片

<?php
/**
 * 公式识别 WebAPI 接口调用示例
 * 运行前：请先填写Appid、APIKey、APISecret
 * 
 * 1.接口文档（必看）：https://www.xfyun.cn/doc/words/formula-discern/API.html
 * 2.错误码链接：https://www.xfyun.cn/document/error-code （错误码code为5位数字）
 * @author iflytek
 */


class itr_teach_test {
    function tocurl($url, $header, $content){
        $ch = curl_init();
        if(substr($url,0,5)=='https'){
            curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false); // 跳过证书检查
            curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);  // 从证书中检查SSL加密算法是否存在
            curl_setopt($ch, CURLOPT_SSLVERSION, 1);
        }
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_URL, $url);
        if (is_array($header)) {
            curl_setopt($ch, CURLOPT_HTTPHEADER, $header);
        }
        curl_setopt($ch, CURLOPT_POST, true);
        if (!empty($content)) {
            if (is_array($content)) {
                curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($content));
            } else if (is_string($content)) {
                curl_setopt($ch, CURLOPT_POSTFIELDS, $content);
            }
        }
        $response = curl_exec($ch);
        $error=curl_error($ch);
        //var_dump($error);
        if($error){
            die($error);
        }
        $header = curl_getinfo($ch);

        curl_close($ch);
        $data = array('header' => $header,'body' => $response);
        return $data;
    }
    function xfyun($pic,$jpg) {
		//在控制台-我的应用-公式识别获取
        $app_id = "xxxxxx";
		//在控制台-我的应用-公式识别获取
        $api_sec = "xxxxxx";
		//在控制台-我的应用-公式识别获取
        $api_key = "xxxxxx";
		//图片路径
        $resource = $jpg;

        $url = "https://rest-api.xfyun.cn/v2/itr";

        //body组装
        $body = json_encode($this->getBody($app_id,  $resource));

        // 组装http请求头
        //$date = gmstrftime("%a, %d %b %Y %H:%M:%S %Z", time());
		$date =gmdate('D, d M Y H:i:s') . ' GMT';
		
        $digestBase64  = "SHA-256=".base64_encode(hash("sha256", $body, true));
		
        $builder = sprintf("host: %s
date: %s
POST /v2/itr HTTP/1.1
digest: %s", "rest-api.xfyun.cn", $date, $digestBase64);

        $sha = base64_encode(hash_hmac("sha256", $builder, $api_sec, true));

        $authorization = sprintf("api_key=\"%s\", algorithm=\"%s\", headers=\"%s\", signature=\"%s\"", $api_key, "hmac-sha256", "host date request-line digest", $sha);

        $header = [
            "Authorization: ".$authorization,
            'Content-Type: application/json',
            'Accept: application/json,version=1.0',
            'Host: rest-api.xfyun.cn',
            'Date: '.$date,
            'Digest: '.$digestBase64
        ];

        $response = $this->tocurl($url, $header, $body);

        //var_dump($response['body']);
        $res = json_decode($response['body'], true);//转换为数组
        $content = $res['data']['region'][0]['recog']['content'];
        $content = str_replace("  ", "", $content);
        $content = str_replace("ifly-latex-begin", "", $content);
        $content = str_replace("ifly-latex-end", "", $content);
        header("content-type: application/json");
        if($res['code']=='0'){
            $code='200';
        }else{
            $code='202';
        }
        $json_return = array(
            "code" => $code,
            "src" => $pic,
            "dst" => ltrim($content)
        );
        $result = json_encode($json_return, JSON_UNESCAPED_UNICODE);
        echo $result;
    }

    function getBody($app_id, $resource) {
        $common_param = [
            'app_id'   => $app_id
        ];
        $image_data = fread(fopen($resource, 'r'), filesize($resource));
        $base64_image = chunk_split(base64_encode($image_data));

        $data = [
            'image' => $base64_image
        ];

        return $body = [
            'common' => $common_param,
            'business' => [
                'ent' => 'teach-photo-print',
                'aue'      => 'raw'
            ],
            'data' => $data
        ];
    }
}

/*
*@通过curl方式获取指定的图片到本地
*@ 完整的图片地址
*@ 要存储的文件名
*/
function getImg($url = "", $filename = ""){
    //去除URL连接上面可能的引号
    $hander = curl_init();
    $fp = fopen($filename, 'wb');
    curl_setopt($hander, CURLOPT_URL, $url);
    curl_setopt($hander, CURLOPT_FILE, $fp);
    curl_setopt($hander, CURLOPT_HEADER, 0);
    curl_setopt($hander, CURLOPT_FOLLOWLOCATION, 1);
    curl_setopt($hander, CURLOPT_TIMEOUT, 60);
    curl_exec($hander);
    curl_close($hander);
    fclose($fp);
    return true;
}

header('Access-Control-Allow-Origin:*');
header('Content-type: application/json');

$pic=isset($_GET['pic'])? $_GET['pic'] :null; 
if(empty($pic)){die("请传入图片参数");}
$time = gmdate('H-i-s', time() + 3600 * 8);   
$jpg = $time.'.jpg';
getImg($pic,$jpg);

$a = new itr_teach_test();
$a->xfyun($pic,$jpg);
unlink($jpg);

Demo：https://api.szfx.top/api/xfitr.html

构建的在线公式识别网站：https://tool.szfx.top/itr