使用PHP eval运行代码导致致命错误：无法重新声明函数

Question

I have a PHP script that selects one of many PHP code snippets from the database and executes it using eval. In some cases if two code snippets try to declare a function with the same name, I get the fatal error "cannot redeclare function". Editing the function names in the code snippets is not an option. Is there some way to create a scope or maybe have the functions overwrite each other? Or any other better ideas?

Thanks.

Edit: Loops this code.

ob_start();
try {
    $result = eval($source_code);
} catch(Exception $e) {
    echo "error";
}
$error = ob_get_clean();

Answer 1

You have three choices, really.

function_exists()

// this will check for the function's existence before trying to declare it
if(!function_exists('cool_func')){
    function cool_func(){
        echo 'hi';
    }
}

// business as usual
cool_func();

Assign function to a variable

// this will automatically overwrite any uses of $cool_func within the current scope
$cool_func = function(){
    echo 'hi';
}

// call it like this
$cool_func();

Namespacing in PHP >= 5.3.0

/* WARNING: this does not work */
/* eval() operates in the global space */
namespace first {
    eval($source_code);
    cool_func();
}

namespace second {
    eval($source_code);
    cool_func();
}

// like this too
first\cool_func();
second\cool_func();

/* this does work */
namespace first {
    function cool_func(){echo 'hi';}
    cool_func();
}

namespace second {
    function cool_func(){echo 'bye';}
    cool_func();
}

---

With the second example you would need to eval() the DB code once within every scope which you need to use $cool_func, see below:

eval($source_code);

class some_class{
    public function __construct(){
        $cool_func(); // <- produces error
    }
}

$some_class = new some_class(); // error shown

class another_class{
    public function __construct(){
        eval($source_code); // somehow get DB source code in here :)
        $cool_func(); // works
    }
}

$another_class = new another_class(); // good to go