[php] "Fatal error: Cannot redeclare <function>"

I have a function(this is exactly how it appears, from the top of my file):

<?php
//dirname(getcwd());
function generate_salt()
{
    $salt = '';

    for($i = 0; $i < 19; $i++)
    {
        $salt .= chr(rand(35, 126));
    }

    return $salt;
}
...

And for some reason, I keep getting the error:

Fatal error: Cannot redeclare generate_salt() (previously declared in /Applications/MAMP/htdocs/question-air/includes/functions.php:5) in /Applications/MAMP/htdocs/question-air/includes/functions.php on line 13

I cannot figure out why or how such an error could occur. Any ideas?

If your having a Wordpress theme problem it could be because although you have renamed the theme in your wp_options table you havn't renamed the stylesheet. I struggled with this.

you can check first if name of your function isn`t exists or not before you write function By

  if (!function_exists('generate_salt'))
{
    function generate_salt()
    {
    ........
    }
}

OR you can change name of function to another name

You're probably including the file functions.php more than once.

or you can't create function in loop

• such as

  for($i=1; $i<5; $i++) { function foo() { echo 'something'; } }

foo();
//It will show error regarding redeclaration

Another possible reason for getting that error is that your function has the same name as another PHP built-in function. For example,

function checkdate($date){
   $now=strtotime(date('Y-m-d H:i:s'));
   $tenYearsAgo=strtotime("-10 years", $now);
   $dateToCheck=strtotime($date);
   return ($tenYearsAgo > $dateToCheck) ? false : true;
}
echo checkdate('2016-05-12');

where the checkdate function already exists in PHP.

I want to add my 2 cent experience that might be helpful for many of you.

If you declare a function inside a loop (for, foreach, while), you will face this error message.

Solution 1

Don't declare function inside a loop (like foreach, for, while...) ! Declare before them.

Solution 2

You should include that file (wherein that function exists) only once. So,
instead of :  include ("functions.php");
use:             include_once("functions.php");

Solution 3

If none of above helps, before function declaration, add a check to avoid re-declaration:

if (!function_exists('your_function_name'))   {
  function your_function_name()  {
    ........
  }
}

I'd recommend using get_included_files - as Pascal says you're either looking at the wrong file somehow or this function is already defined in a file that's been included.

require_once is also useful if the file you're attempting to include is essential.

I don't like function_exists('fun_name') because it relies on the function name being turned into a string, plus, you have to name it twice. Could easily break with refactoring.

Declare your function as a lambda expression (I haven't seen this solution mentioned):

$generate_salt = function()
{
    ...
};

And use thusly:

$salt = $generate_salt();

Then, at re-execution of said PHP code, the function simply overwrites the previous declaration.

I had the same problem. And finally it was a double include. One include in a file named X. And another include in a file named Y. Knowing that in file Y I had include ('X')

Since the code you've provided does not explicitly include anything, either it is being incldued twice, or (if the script is the entry point for the code) there must be a auto-prepend set up in the webserver config / php.ini or alternatively you've got a really obscure extension loaded which defines the function.

I had strange behavor when my *.php.bak (which automaticly was created by notepad) was included in compilation. After I removed all *.php.bak from folder this error was gone. Maybe this will be helpful for someone.

I had this pop up recently where a function was being called prior to its definition in the same file, and it didnt have the returned value assigned to a variable. Adding a var for the return value to be assigned to made the error go away.

In my case it was because of function inside another function! once I moved out the function, error was gone , and everything worked as expected.

This answer explains why you shouldn't use function inside function.

This might help somebody.

This errors says your function is already defined ; which can mean :

• you have the same function defined in two files
• or you have the same function defined in two places in the same file
• or the file in which your function is defined is included two times (so, it seems the function is defined two times)

I think your facing problem at 3rd position the script including this file more than one time.So, you can solve it by using require_once instead of require or include_once instead of include for including your functions.php file -- so it cannot be included more than once.

means you have already created a class with same name.

For Example:

class ExampleReDeclare {}

// some code here

class ExampleReDeclare {}

That second ExampleReDeclare throw the error.