PHPのお勉強！

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    実行演算子

    PHP は 1 種類の実行演算子、バッククォート (``) をサポートします。 シングルクォートではないことに注意してください! PHP は、バッククォートの 中身をシェルコマンドとして実行しようとします。出力が返されます (すなわち、出力を単にダンプするのではなく、変数に代入することが できます) 。 バッククォート演算子の使用は shell_exec() と等価です。

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

    注意:

    バッククォート演算子は、 shell_exec() が無効な場合は無効となります。

    注意:

    他の言語とは異なり、 ダブルクォートで囲まれた文字列の中でのバッククォート演算子には何の効力もありません。

    参考

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    User Contributed Notes 3 notes

    up
    153
    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
    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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