将PHP变量传递给Javascript，然后将其保存到文本文件中

<script>
   var phpVariable = "<?php echo $phpVariable; ?>";
   // 或者使用隐藏的input元素
   document.getElementById("hiddenInput").value = "<?php echo $phpVariable; ?>";
</script>

var textToSave = phpVariable; // 从PHP变量中获取的值

var blob = new Blob([textToSave], {type: "text/plain;charset=utf-8"});

var downloadLink = document.createElement("a");
downloadLink.download = "filename.txt";
downloadLink.innerHTML = "Download File";

if (window.URL != null) {
  // 使用URL.createObjectURL方法创建URL
  downloadLink.href = window.URL.createObjectURL(blob);
} else {
  // 兼容性处理
  downloadLink.href = window.URL.createObjectURL(blob);
  downloadLink.onclick = destroyClickedElement;
  downloadLink.style.display = "none";
  document.body.appendChild(downloadLink);
}

downloadLink.click();