php中exec（）的输出是空数组

Question

I have the following code to execute mysqldump using exec(). It was not working and I wanted figure out what output the command line throws. So I printed $output and $worked. But all I get is 1 and an empty array.

Accordong to manual: If the output argument is present, then the specified array will be filled with every line of output from the command. But why is this throwing an empty array? I am including 2>&1 at the end of command as some post suggested, but still not working. I want to know what the terminal is outputting when this command is being executed.

And what does $worked outputting 1 mean?

Any help will be greatly appreciated!

Script:

$command='mysqldump --opt -u ' .$db['username'] .' -p' .$db['password'] .' --databases ' .$db['database'] .' > '.$mysqlExportPath .' 2>&1';
$output=array();
exec($command,$output,$worked);

print $worked.'<br>';
print_r($output);

Outputs:

1
Array ( ) 

Answer 1

I want to know what the terminal is outputting when this command is being executed.

Nothing! (And had you simply tried it yourself you'd have seen that immediately). Your command directs the result of mysqldump to the file at the path denoted by $mysqlExportPath. I don't know why you expect it to go to stdout instead.

Perhaps some line breaks would help to make your code a little (no, substantially!) more readable:

$command
  = 'mysqldump --opt'
  . ' -u ' . $db['username']
  . ' -p' . $db['password']
  . ' --databases ' . $db['database']
  . ' > ' . $mysqlExportPath   // <---- Here you go!
  . ' 2>&1';

Remove the redirection, or find the data inside the file $mysqlExportPath; your call!