Javascript base64解码图像不下载

我使用以下脚本将html画布转换为png，并让客户端下载它，而无需将图像保存到服务器。这些脚本在xampp和服务器cuccfree.cc中工作。但是相同的脚本在我需要托管的服务器中不起作用

Javascript

         fname = fname || 'picture';

        var data = cnvs.toDataURL("image/png");
        data = data.substr(data.indexOf(',') + 1).toString();

        var dataInput = document.createElement("input") ;
        dataInput.setAttribute("name", 'imgdata') ;
        dataInput.setAttribute("value", data);
        dataInput.setAttribute("type", "hidden");

        var nameInput = document.createElement("input") ;
        nameInput.setAttribute("name", 'name') ;
        nameInput.setAttribute("value", fname + '.png');

        var myForm = document.createElement("form");
        myForm.method = 'post';
        myForm.action = url;
        myForm.appendChild(dataInput);
        myForm.appendChild(nameInput);

        document.body.appendChild(myForm) ;
        myForm.submit() ;
        document.body.removeChild(myForm) ;

<?php
    # we are a PNG image
    header('Content-type: image/png');

    # we are an attachment (eg download), and we have a name
    header('Content-Disposition: attachment; filename="' . $_POST['name'] .'"');

    #capture, replace any spaces w/ plusses, and decode
    $encoded = $_POST['imgdata'];
    $encoded = str_replace(' ', '+', $encoded);
    $decoded = base64_decode($encoded);

    #write decoded data
    echo $decoded;
?>

PHP scipt

         fname = fname || 'picture';

        var data = cnvs.toDataURL("image/png");
        data = data.substr(data.indexOf(',') + 1).toString();

        var dataInput = document.createElement("input") ;
        dataInput.setAttribute("name", 'imgdata') ;
        dataInput.setAttribute("value", data);
        dataInput.setAttribute("type", "hidden");

        var nameInput = document.createElement("input") ;
        nameInput.setAttribute("name", 'name') ;
        nameInput.setAttribute("value", fname + '.png');

        var myForm = document.createElement("form");
        myForm.method = 'post';
        myForm.action = url;
        myForm.appendChild(dataInput);
        myForm.appendChild(nameInput);

        document.body.appendChild(myForm) ;
        myForm.submit() ;
        document.body.removeChild(myForm) ;

<?php
    # we are a PNG image
    header('Content-type: image/png');

    # we are an attachment (eg download), and we have a name
    header('Content-Disposition: attachment; filename="' . $_POST['name'] .'"');

    #capture, replace any spaces w/ plusses, and decode
    $encoded = $_POST['imgdata'];
    $encoded = str_replace(' ', '+', $encoded);
    $decoded = base64_decode($encoded);

    #write decoded data
    echo $decoded;
?>

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我建议您在使用的不同服务器中检查php.ini中的php扩展。可能是生产服务器中缺少扩展