PHP Filemtime（）中的警告＆不能修改标题信息 - 标题已发送错误

Question

在@James的帮助下，图像生成器处于良好状态。现在，当文件或文件夹不存在时，图像引擎会输出一个微小但奇怪的错误。确实应该有和错误，但我不确定它应该是下面的这一个。下面是当谷歌试图通过imgcpu.php缩略图生成器来获取一个老不存在的文件夹/ image.jpg的会发生什么：

[20:24:25] PHP Warning: filemtime() [<a href='function.filemtime'>function.filemtime</a>]: stat failed for old_folder/old-image.jpg in imgcpu.php on line 802 
[20:24:25] PHP Warning: Cannot modify header information - headers already sent by (output started at imgcpu.php:802) in imgcpu.php on line 201 

[20:26:31] PHP Warning: filemtime() [<a href='function.filemtime'>function.filemtime</a>]: stat failed for old_folder/old-image.jpg in imgcpu.php on line 802 
[20:26:31] PHP Warning: Cannot modify header information - headers already sent by (output started at imgcpu.php:802) in imgcpu.php on line 201 

[20:28:24] PHP Warning: filemtime() [<a href='function.filemtime'>function.filemtime</a>]: stat failed for old_folder/old-image.jpg in imgcpu.php on line 802 
[20:28:24] PHP Warning: Cannot modify header information - headers already sent by (output started at imgcpu.php:802) in imgcpu.php on line 201 

[20:31:03] PHP Warning: filemtime() [<a href='function.filemtime'>function.filemtime</a>]: stat failed for old_folder/old-image.jpg in imgcpu.php on line 802 
[20:31:03] PHP Warning: Cannot modify header information - headers already sent by (output started at imgcpu.php:802) in imgcpu.php on line 201 

看来，线201和802有什么关系呢：

line 201**  header('HTTP/1.1 400 Bad Request'); 
line 202  die($message); 
.... 
line 801  header("Content-type: " . $this->_mime); 
line 802**  $last_modified = filemtime($source); 

问题：错误是否正确？或者应该以某种方式解决警告？如果是这样，怎么样？

Answer 1

我想，如果该文件不存在，您不应该尝试获取文件的上次修改日期。

您应该检查文件是否存在，首先使用file_exists()函数。

我想你应该使用这样的事情：

if (file_exists($source)) { 
    $last_modified = filemtime($source); 
    // Use the $last_modified variable 
} 
else { 
    // the file doesn't exist => 404 
    header('HTTP/1.1 404 Not Found'); 
    die; 
}