Access a global variable in a PHP function

Question

According to the most programming languages scope rules  I can access variables that are defined outside of functions inside them  but why doesn t this code work    lt  php      data    My data        function menugen             echo        data                   menugen      gt    The output is

User · Answer

For many years I have always used this format:

<?php
    $data = "Hello";

    function sayHello(){
        echo $GLOBALS["data"];
    }

    sayHello();
?>

I find it straightforward and easy to follow. The $GLOBALS is how PHP lets you reference a global variable. If you have used things like $_SERVER, $_POST, etc. then you have reference a global variable without knowing it.

User · Answer

You need to pass the variable into the function    data    My data    function menugen  data        echo  data

User · Answer

Another way to do it    lt  php   data    My data     menugen   function   use   data         echo      data           menugen      UPDATE 2020-01-13  requested by Peter Mortensen  As of PHP 5 3 0 we have anonymous functions support that can create closures  A closure can access the variable which is created outside of its scope   In the example  the closure is able to access  data because it was declared in the use clause

User · Answer

It s a matter of scope  In short  global variables should be avoided so   You either need to pass it as a parameter    data    My data    function menugen  data        echo  data      Or have it in a class and access it  class MyClass       private  data            function menugen                 echo this- gt data             See  MatteoTassinari answer as well  as you can mark it as global to access it  but global variables are generally not required  so it would be wise to re-think your coding

User · Answer

You can do one of the following    lt  php      data    My data        function menugen             global  data          echo        data                   menugen      Or   lt  php      data    My data        function menugen             echo        GLOBALS  data                     menugen      That being said  overuse of globals can lead to some poor code  It is usually better to pass in what you need  For example  instead of referencing a global database object you should pass in a handle to the database and act upon that  This is called dependency injection  It makes your life a lot easier when you implement automated testing  which you should

User · Answer

PHP can be frustrating for this reason  The answers above using global did not work for me  and it took me awhile to figure out the proper use of use  This is correct   functionName   function  stuff  use   globalVar       do stuff    output    functionName  stuff    otherOutput    functionName  otherStuff    This is incorrect  function functionName  stuff  use   globalVar       do stuff    output   functionName  stuff    otherOutput   functionName  otherStuff    Using your specific example       data    My data         menugen   function   use   data            echo  quot   quot     data    quot   quot               menugen

User · Answer

If you want  you can use the  define  function  but this function creates a constant which can t be changed once defined    lt  php     define  GREETING    Welcome to W3Schools com          function myTest             echo GREETING             myTest      gt    PHP Constants

User · Answer

lt  php       data    My data         menugen   function   use   data             echo     data                  menugen      gt    You can also simplify   echo        data         to  echo    data

User · Answer

It is not working because you have to declare which global variables you ll be accessing    data    My data    function menugen         global  data      lt -- Add this line      echo        data           menugen      Otherwise you can access it as  GLOBALS  data    See Variable scope   Even if a little off-topic  I d suggest you avoid using globals at all and prefer passing as parameters

[php] Access a global variable in a PHP function

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