Getting Global Access | Spring Into PHP 5

You already know that variables inside a function have their own scope and don't mix with variables outside the function:

 $value = 5; echo "At script level, \$value = ", $value, "<BR>"; local_scope(); echo "At script level again, \$value still = ", $value, "<BR>"; function local_scope() {     $value = 1000000;     echo "But in the function, \$value = ", $value, "<BR>"; }

But what if you actually wanted to access the value of a script-level variable, called a global variable, inside a function? For example, if you set $value to 5 at the script level, you might try to access its value inside a function like this:

 $value = 5; function global_scope() {     echo "\$value = ", $value, "<BR>"; }

However, this won't work (although it will in some languages) because PHP wants to prevent unintentional conflict between global and local variables. If you want to access a global variable in a function, you have to explicitly say so. One way of doing this is with the global keyword, as you see in phpglobal.php, Example 4-9.

Example 4-9. Using global scope data in functions, phpglobal.php

 <HTML>         <HEAD>             <TITLE>                 Using global and local scope             </TITLE>         </HEAD>         <BODY>             <H1>                  Using global and local scope             </H1>             <?php                 $value = 5;                 echo "At script level, \$value = ", $value, "<BR>";                 local_scope();                 global_scope();                 echo "At script level again, \$value still = ", $value, "<BR>";                 function local_scope()                 {                     $value = 1000000;                     echo "But in the function, \$value = ", $value, "<BR>";                 }                 function global_scope()                 {                     global $value;                     echo "Using the global scope, \$value = ", $value, "<BR>";                 }             ?>     </BODY> </HTML>

After you indicate that you want access to the global value in $value, PHP gives it to you, as you can see in Figure 4-9.

Figure 4-9. Using global and local scope.

You can also access global data by using the special PHP-defined $GLOBALS array. Here's how you would do that in this example:

 function global_scope() {     echo "Using the global scope, \$value = ", $GLOBALS["value"], "<BR>"; }