Question

I have spend hours on google and still can’t find a php doc explain this. Can someone point me to the right link please? Got this code from a SVN:

<?php
  echo `snv up`;

the one thing I can’t understand is the ` mark… It is not a quotation mark.. it is the most left-top key on a qwerty keyboard.

It seems that this will execute “svn up” as shell command, but what’s the difference from exec(“snv up”) then? Anyone can point me to a credible source of explanation?

Answer 1

Backticks are the PHP shell execution operator, and they’re the same as shell_exec (not exec). From the Execution Operators documentation:

PHP supports one execution operator: backticks (`). Note that these are not single-quotes! PHP will attempt to execute the contents of the backticks as a shell command; the output will be returned (i.e., it won’t simply be dumped to output; it can be assigned to a variable). Use of the backtick operator is identical to shell_exec().