Operador de ejecución

    PHP soporta un operador de ejecución: comillas invertidas (``). Téngase en cuenta que no se trata de comillas simples. PHP intenta ejecutar el contenido de estas comillas invertidas como un comando shell. El resultado será devuelto (es decir: no será simplemente enviado a la salida estándar, puede ser asignado a una variable). Utilizar las comillas invertidas equivale a utilizar la función shell_exec().

    Ejemplo #1 Operador de comillas invertidas

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

    Nota:

    Este operador está desactivado cuando la función shell_exec() está desactivada.

    Nota:

    A diferencia de otros lenguajes, las comillas invertidas no tienen un significado especial en una cadena rodeada de comillas dobles.

    Ver también

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    User Contributed Notes 3 notes

    up
    153
    robert
    19 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
    114
    ohcc at 163 dot com
    8 years ago
    You can use variables within a pair of backticks (``).

    <?php
    $host     = 'www.wuxiancheng.cn';
    echo `    ping -n 3 {$host}`;
    ?>
    up
    4
    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.
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