Description
mixed
eval ( string code_str )
eval() evaluates the string given in
code_str as PHP code. Among other things,
this can be useful for storing code in a database text field for
later execution.
There are some factors to keep in mind when using
eval(). Remember that the string passed must
be valid PHP code, including things like terminating statements
with a semicolon so the parser doesn't die on the line after the
eval(), and properly escaping things in
code_str.
Also remember that variables given values under
eval() will retain these values in the main
script afterwards.
A return statement will terminate the evaluation of
the string immediately. As of PHP 4, eval() returns
NULL unless return is called in the evaluated
code, in which case the value passed to return is
returned. In case of a parse error in the evaluated code,
eval() returns FALSE.
In case of a fatal error in the evaluated code, the whole script exits.
In PHP 3, eval() does not return a value.
Пример 1.
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";
?>
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Результат выполнения данного примера: This is a $string with my $name in it.
This is a cup with my coffee in it. |
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Подсказка: Как и с любой другой функцией, осуществляющей
вывод непосредственно в браузер, вы можете использовать функции контроля вывода, чтобы перехватывать
выводимые этой функцией данные и сохранять их, например, в
string.
See also call_user_func().