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In PHP, global variables are variables accessible in functions, classes, and scripts. These variables can be declared and initialized by specifying the $GLOBALS array, or they can be declared as global variables inside the function. However, it is not easy to access global variables in a function, because the function is a local scope structure, so how to access global variables inside the function?
One way is to use the $GLOBALS array. For example:
<?php $number = 50; function change_number() { global $number; $number = 100; } change_number(); echo $number; // 输出: 100 ?>
In the above example, we have used the global
keyword to declare $number
as a global variable, so inside the function $number After the value of
is modified, it also changes outside the function.
Another approach is to use $GLOBALS
super global arrays. For example:
<?php $number = 50; function change_number() { $GLOBALS['number'] = 100; } change_number(); echo $number; // 输出: 100 ?>
In the above example, the $number
key value in $GLOBALS
corresponds to the global variable $number
. When we modify the value of $GLOBALS['number']
inside the function, the value of the global variable $number
is also modified.
It should be noted that excessive use of global variables may make the code difficult to maintain. If you need to use a lot of variables inside a function, it's better to pass them into the function from outside to avoid dependencies between functions.
To sum up, you can access and modify global variables using the global
keyword or the $GLOBALS
array. However, you need to use global variables with caution and use variables as function parameters whenever possible to avoid code that is cluttered and difficult to maintain.
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