file_get_contents解决方案对于大型文件而言效率不高。此解决方案可能需要更长的时间，具体取决于需要添加的数据量（实际上越多越好），但是它不会消耗内存。

<?php

$cache_new = "Prepend this"; // this gets prepended
$file = "file.dat"; // the file to which $cache_new gets prepended

$handle = fopen($file, "r+");
$len = strlen($cache_new);
$final_len = filesize($file) + $len;
$cache_old = fread($handle, $len);
rewind($handle);
$i = 1;
while (ftell($handle) < $final_len) {
  fwrite($handle, $cache_new);
  $cache_new = $cache_old;
  $cache_old = fread($handle, $len);
  fseek($handle, $i * $len);
  $i++;
}
?>