eval

Evaluate a string as PHP code

&reftitle.description; `mixed` `eval` `string` `code`

Evaluates the given `code` as PHP.

The code being evaluated inherits the variable scope of the line on which the `eval` call occurs. Any variables available at that line will be available for reading and modification in the evaluated code. However, all functions and classes defined will be defined in the global namespace. In other words, the compiler considers the evaluated code as if it were a separate included file.

The `eval` language construct is very dangerous because it allows execution of arbitrary PHP code. Its use thus is discouraged. If you have carefully verified that there is no other option than to use this construct, pay special attention not to pass any user provided data into it without properly validating it beforehand.

&reftitle.parameters;

`code`

- Valid PHP code to be evaluated.

  The code must not be wrapped in opening and closing PHP tags, i.e. `'echo "Hi!";'` must be passed instead of `'<?php echo "Hi!"; ?>'`. It is still possible to leave and re-enter PHP mode though using the appropriate PHP tags, e.g. `'echo "In PHP mode!"; ?>In HTML mode!<?php echo "Back in PHP mode!";'`.

  Apart from that the passed code must be valid PHP. This includes that all statements must be properly terminated using a semicolon. `'echo "Hi!"'` for example will cause a parse error, whereas `'echo "Hi!";'` will work.

  A `return` statement will immediately terminate the evaluation of the code.

  The code will be executed in the scope of the code calling `eval`. Thus any variables defined or changed in the `eval` call will remain visible after it terminates.

&reftitle.returnvalues;

`eval` returns &null; unless `return` is called in the evaluated code, in which case the value passed to `return` is returned. As of PHP 7, if there is a parse error in the evaluated code, `eval` throws a ParseError exception. Before PHP 7, in this case `eval` returned &false; and execution of the following code continued normally. It is not possible to catch a parse error in `eval` using `set_error_handler`.

&reftitle.examples;

### `eval` example - simple text merge

    <?php
    $string = 'cup';
    $name = 'coffee';
    $str = 'This is a $string with my $name in it.';
    echo $str. "\n";
    eval("\$str = \"$str\";");
    echo $str. "\n";
    ?>

&example.outputs;

    This is a $string with my $name in it.
    This is a cup with my coffee in it.

&reftitle.notes; ¬e.language-construct; &tip.ob-capture;

In case of a fatal error in the evaluated code, the whole script exits.

&reftitle.seealso;

- `call_user_func`