Global variables in PHP

Question

I'm writing a script that will select a random word from among words in an input file, multiple times. Now calling file() multiple times seems inefficient, so I'm thinking of having a global array for the words from the file and a function that will load the file into the array (called before selecting random words). Why doesn't it work?

global $words;

function init_words($file)
{
    $words = file($file);
    $count = count($words);
    echo "$count words<br>\n"; // "3 words"
}

init_words("/foo/bar");
$count = count($words);
echo "$count words<br>\n"; // "0 words"

The semantics in PHP are a bit different. Global variables aren't what they are in C for example. They need to be invited into the function scope. — mario, Mar 30 '11 at 22:05
*(related)* [PHP Global in Functions](http://stackoverflow.com/questions/5166087/php-global-in-functions) — Gordon, Mar 30 '11 at 22:22

Treffynnon · Accepted Answer · 2011-03-30T22:04:51.230

You need to declare $words global within the function itself. See:

$words = '';

function init_words($file)
{
    global $words;
    $words = file($file);
    $count = count($words);
    echo "$count words<br>\n"; // "3 words"
}

I suggest you review the variable scope chapter in the PHP manual.

As an aside I would never write this code in this way. Avoid globals unless they are absolutely necessary.

I would write your code this way to avoid this problem:

function init_words($file)
{
    $words = file($file);
    $count = count($words);
    echo "$count words<br>\n"; // "3 words"
    return $words;
}

$words = init_words("/foo/bar");
$count = count($words);
echo "$count words<br>\n"; // "3 words"

Please see the returning values chapter in the PHP manual for more information on this.

This. `global` works differently then what most people expect in PHP. It doesn't define a variable as global scope, instead it says that "for the following scope, I want to use the global version of [var], not a local one." — Mr. Llama, Mar 30 '11 at 22:02

score 2 · Answer 2 · answered Mar 30 '11 at 21:58

$words = null;

function init_words($file)
{
    global $words;
    $words = file($file);
    $count = count($words);
    echo "$count words<br>\n"; // "3 words"
}

init_words("/foo/bar");
$count = count($words);
echo "$count words<br>\n"; // "0 words"

The global part should go inside your function

side note: it is not always the best to use global operators

score 2 · Answer 3 · answered Mar 30 '11 at 21:58

2

You want global $words; inside the function. Better yet, use the superglobal $GLOBALS.

answered Mar 30 '11 at 21:58

phihag

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[Variable scope](http://php.net/manual/en/language.variables.scope.php): Note: Using global keyword outside a function is not an error. It can be used if the file is included from inside a function. – Jared Farrish Mar 30 '11 at 22:01
@Jared Oh, of course, bad choice of words by me. Updated. – phihag Mar 30 '11 at 22:02
@phihag $GLOBALS has got to be the best way of using a global variable inside a function. mitigates spagetti code. something tells me php wants to enforce OO programming. :) – dewd Jan 13 '14 at 15:42

score 0 · Answer 4 · answered Mar 30 '11 at 22:02

0

first you need to store the words in a serialised formant so that means

$file_location = "/foo/bar/words.txt";
$words = array("game", "cool", "why");
$words = serilize($words);
write_words_file($words, $filelocation); //Create the function so it can write to a file

then you will need to edit your init_words

function init_words($file)
{
    global $words;
    $data = file_get_contents($file);
    $words = unserialize($data);
    $count = count($words);
    echo "$count words<br>\n"; // "3 words"
}

init_words("/foo/bar/words.txt");
$count = count($words);
echo "$count words<br>\n"; // "0 words"

answered Mar 30 '11 at 22:02

Vish

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Why do they need to be serialized? The `file()` method the OP is using turns each new line in a file into a item in an array. There is no need for serialisation. – Treffynnon Mar 30 '11 at 22:06
then you dont need to serialize it. – Vish Mar 30 '11 at 22:12

score 0 · Answer 5 · answered Mar 30 '11 at 22:07

Alternately, you could use the following and avoid usage of global altogether:

function init_words($fname)
{
    $w = file($fname, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);  // We don't want the trailing spaces or empty lines.
    $c = count($w);

    return array($w, $c);
}

list($words, $count) = init_words("Some_File.txt");

In such a situation if you ever had to do any manipulation of the list of words, you can handle it all within init_words() as opposed to elsewhere in the script.

Global variables in PHP

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