php eval string as function

Question

What is the best way to go about defining a php function and the call to that function, in a string, and then executing that code i.e., eval? I'm trying to get the length of an encoded uri out of a function defined and called in a string.

$json_arr['my_function'] = "function hashfun1($enc_uri) { return strlen($enc_uri); } hashfun1($enc_uri);";
$hash_func = $json_arr['my_function'];
$hash_val = eval($hash_func);
print_r($hash_val); // should be length of encoded uri but displays "Parse error: syntax error, unexpected '%', expecting '&' or T_VARIABLE"
exit;

Thanks.

I don't understand what you're trying to accomplish with that code. Why do you need `eval()` in the first place? — Amal Murali, Feb 19 '14 at 20:18
Why is your function stored in a string? Where is that string coming from? Remember, "if `eval()` is the answer, you're almost certainly asking the wrong question". — gen_Eric, Feb 19 '14 at 20:19
The function is being returned as a json response from a rest service. I need to use the function returned to get the length of an encoded uri: `function encodeURIComponent($str) { $revert = array('%21'=>'!', '%2A'=>'*', '%27'=>"'", '%28'=>'(', '%29'=>')'); return strtr(rawurlencode($str), $revert); }` — neridaj, Feb 19 '14 at 20:27

score 0 · Answer 1 · edited May 23 '17 at 11:57

0

I guess you want:

$json_arr['my_function'] = "function hashfun1($enc_uri) { return strlen($enc_uri); } hashfun1('" . $enc_uri . '");";

You missed to populate $enc_uri.

Don't do this in production code, although it works. eval() is evil. You have been warned.

edited May 23 '17 at 11:57

Community

1
1

answered Feb 19 '14 at 20:20

hek2mgl

152,036
28
249
266

score 0 · Answer 2 · answered Feb 19 '14 at 20:23

0

you need to escape "$" in double-quoted string. And check number of returns (second for eval):

$json_arr['my_function'] = "function hashfun1(\$enc_uri) { return strlen(\$enc_uri); } return hashfun1(\$enc_uri);";

answered Feb 19 '14 at 20:23

Michael Livach

518
3
13

and why you use eval? It breaks opcode cache and makes sense in rare cases. If you look for dynamic function generation, check this: (old) http://php.net/create_function http://php.net/call_user_func_array (new) http://php.net/manual/en/functions.anonymous.php – Michael Livach Feb 19 '14 at 20:33

score 0 · Answer 3 · answered Feb 19 '14 at 21:08

0

I guess I need to use call_user_func(); This worked for me: $json_arr['my_function'] = function($enc_uri) { return strlen($enc_uri); }; $hash_val = call_user_func($json_arr['my_function'], $enc_uri); print_r($hash_val); exit;

Thanks for the help guys.

answered Feb 19 '14 at 21:08

neridaj

2,143
9
31
62

php eval string as function

3 Answers3