为什么wget backticks shell命令可以在PHP CLI中工作，而不能在PHP脚本中工作？

Question

just for fun I am trying to make wget downloads from php cli (/usr/bin/php -a) and it works:

php > `wget -q -nd -O /Users/user/path/to/file.html http:\/\/host.com/some_file.html`;
php > // a HTML file is downloaded and its content is placed into /Users/user/path/to/file.html

However, when I try to do the same thing from a PHP script, it does not work:

<?php 
 `wget -q -nd -O /Users/user/path/to/file.html http:\/\/host.com/some_file.html`;
 // After requesting the script from the browser and after the script is executed, the file doesn't exist on the specified path

I would like to say that the user which executes apache and therefore PHP server side scripting is the same as the user which executes the php command from the command line (so I guess this should not be a problem of permissions).

Why if I use a .php script and call wget inside the script the file is not saved?

Thanks for the attention!

PS: please, do not tell me that I can use curl for such a task, I know I can, I am just curious to know how can I do something similar without using PHP tools, that's it

Answer 1

use the full path to wget , since the daemon doesn't run .bash_profile .

`/opt/local/bin/wget -q -nd -O /Users/user/path/to/file.html http://host.com/some_file.html`;

BTW, there's no need to escape / in shell commands.

Answer 2

The backtick operator runs a shell command and returns the output from the shell command.

In this situation, simply logging (or if you have to, echo-ing) the result will probably reveal the error. Eg:

$result = `wget -q -nd -O /Users/user/path/to/file.html http:\/\/host.com/some_file.html`;

trigger_error($result, E_USER_NOTICE);