Very basic caching script for PHP

gistfile1.php

<?php

// Example usage

// Set source location
$sourcepath = "http://mysite.com/api/call/something";

// Set cache file
$cacheName = "apicall.cache";

// Set caching time
$ageInSeconds = 3600; // one hour

echo getCacheContent($cacheName, $sourcepath, $ageInSeconds);

simplecache.php

<?php
/**
 * Simple cache method
 *
 * @author: Rutger Laurman
 * Based on http://stackoverflow.com/a/5263017
 */

function getCacheContent($cachefile, $remotepath, $cachetime){

  // Toggle debug mode
  $debug = false;

  // Generate the cache version if it doesn't exist or it's too old!
  if(file_exists($cachefile) && (filemtime($cachefile) > (time() - $cachetime))) {

    if($debug){
      echo "DEBUG: not expired, use cache\n";
    }

  } else {

    if($debug){
      echo "DEBUG: expired, attempt to refresh\n";
    }

    if($contents = @file_get_contents($remotepath)){
      @file_put_contents($cachefile, $contents, LOCK_EX);
      if($debug){
        echo "DEBUG: refresh succes, cache written\n";
      }
    } else {
      if($debug){
        echo "DEBUG: refresh failed, using cache\n";
      }
    }
  }

  // Get contents of cache file
  $fileContents = @file_get_contents($cachefile);

  if($fileContents) {
    return $fileContents;
  } else {
    if($debug){
      echo "DEBUG: failed to get content";
    }
  }
}

I would at least pass a user agent so you don't get blocked by the remote host

<?php

function getCacheContent($cachefile, $remotepath, $cachetime){

    // Generate the cache version if it doesn't exist or it's too old!
    if( ! file_exists($cachefile) OR (filemtime($cachefile) < (time() - $cachetime))) {

        $options = array(
            'method' => "GET",
            'header' => "Accept-language: en\r\n" .
            "User-Agent: Mozilla/5.0 (Windows; U; MSIE 7.0; Windows NT 6.0; en-US)\r\n"
        );

        $context = stream_context_create(array('http' => $options));
        $contents = file_get_contents($remotepath, false, $context);

        file_put_contents($cachefile, $contents, LOCK_EX);
        return $contents;
    }

    return file_get_contents($cachefile);
}