Just a general usage note. I had a very difficult time solving a problem with my script, when I accidentally put one of these backticks at the beginning of a line, like so:
[lots of code]
` $URL = "blah...";
[more code]
Since the backtick is right above the tab key, I probably just fat-fingered it while indenting the code.
What made this so hard to find, was that PHP reported a parse error about 50 or so lines *below* the line containing the backtick. (There were no other backticks anywhere in my code.) And the error message was rather cryptic:
Parse error: parse error, expecting `T_STRING' or `T_VARIABLE' or `T_NUM_STRING' in /blah.php on line 446
Just something to file away in case you're pulling your hair out trying to find an error that "isn't there."Извршување
Почист и полокален преглед на PHP референцата, со задржана структура од PHP.net и подобра читливост за примери, секции и белешки.
Извршување
Референца за `language.operators.execution.php` со подобрена типографија и навигација.
Оператори за извршување
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().
Пример #1 Оператор Backtick
<?php
$output = `ls -al`;
echo "<pre>$output</pre>";
?>Забелешка:
Операторот backtick е оневозможен кога shell_exec() е оневозможено.
Забелешка:
За разлика од некои други јазици, backticks немаат посебно значење во низите со двојни наводници.
Дневник на промени
| Верзија | = NULL |
|---|---|
| 8.5.0 | Операторот backtick како псевдоним за shell_exec() е укинат. |
Белешки од корисници 3 белешки
You can use variables within a pair of backticks (``).
<?php
$host = 'www.wuxiancheng.cn';
echo `ping -n 3 {$host}`;
?>If you want to avoid situations like the one described by @robert you may want to disable `shell_exec` and -as a consequence- the backtick operator.
To do this just edit the `php.ini` file and add `shell_exec` to the `disable_functions` setting:
; This directive allows you to disable certain functions.
; It receives a comma-delimited list of function names.
; https://php.net/disable-functions
disable_functions = "shell_exec"
Then you can still use `exec()` to run terminal commands.