用PHP读取flv文件的播放时间长度

<?php 
// +----------------------------------------------------------------------+ 
// | PHP version 4&5 | 
// +----------------------------------------------------------------------+ 
// | Copyright (c) 2007 [e-mail] | 
// +----------------------------------------------------------------------+ 
// | This source file's function is to get the time length of flv | 
// | main function getTime param:$name The flv file you want to get | 
// +----------------------------------------------------------------------+ 
function BigEndian2Int($byte_word, $signed = false) { 
$int_value = 0; 
$byte_wordlen = strlen($byte_word); 
for ($i = 0; $i < $byte_wordlen; $i++) { 
$int_value += ord($byte_word{$i}) * pow(256, ($byte_wordlen - 1 - $i)); 
} 
if ($signed) { 
$sign_mask_bit = 0x80 << (8 * ($byte_wordlen - 1)); 
if ($int_value & $sign_mask_bit) { 
$int_value = 0 - ($int_value & ($sign_mask_bit - 1)); 
} 
} 
return $int_value; 
} 
function getTime($name){ 
if(!file_exists($name)){ 
return; 
} 
$flv_data_length=filesize($name); 
$fp = @fopen($name, 'rb'); 
$flv_header = fread($fp, 5); 
fseek($fp, 5, SEEK_SET); 
$frame_size_data_length =BigEndian2Int(fread($fp, 4)); 
$flv_header_frame_length = 9; 
if ($frame_size_data_length > $flv_header_frame_length) { 
fseek($fp, $frame_size_data_length - $flv_header_frame_length, SEEK_CUR); 
} 
$duration = 0; 
while ((ftell($fp) + 1) < $flv_data_length) { 
$this_tag_header = fread($fp, 16); 
$data_length = BigEndian2Int(substr($this_tag_header, 5, 3)); 
$timestamp = BigEndian2Int(substr($this_tag_header, 8, 3)); 
$next_offset = ftell($fp) - 1 + $data_length; 
if ($timestamp > $duration) { 
$duration = $timestamp; 
} 
fseek($fp, $next_offset, SEEK_SET); 
} 
fclose($fp); 
return $duration; 
} 
?>