Operadores de Execução

O PHP suporta um operador de execução: acentos graves (``). Note que não são aspas simples! O PHP tentará executar o conteúdo dentro dos acentos graves como um comando do shell; a saída será retornada (isto é, ela não será simplesmente mostrada na tela; ela pode ser atribuída a uma variável). A utilização do operador acento grave é idêntica a da função shell_exec().

<?php
$output
= `ls -al`;
echo
"<pre>$output</pre>";
?>

Nota:

O operador de execução fica desabilitado quando shell_exec() está desabilitado.

Nota:

Ao contrário de outras linguagens, acentos graves não tem sentido especial dentro de strings delimitadas por aspas.

add a note add a note

User Contributed Notes 3 notes

up
141
robert
18 years ago
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."
up
98
ohcc at 163 dot com
7 years ago
You can use variables within a pair of backticks (``).

<?php
    $host
= 'www.wuxiancheng.cn';
    echo `
ping -n 3 {$host}`;
?>
up
0
paolo.bertani
2 years ago
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.
To Top