To access global variables in PHP, you need to use the global keyword or $GLOBALS array. Use the global keyword to declare global variables in a function, such as: global $var;, which is suitable for situations where there are fewer variables, which have intuitive advantages but are prone to pollution; while the $GLOBALS array is directly accessed through $GLOBALS['var'], without declaration, suitable for multivariables but poor readability. It is recommended to avoid abuse of global variables to reduce maintenance difficulties and pay attention to naming conflicts. It is recommended to replace them with parameter passing or class encapsulation.
In PHP, if you want to access global variables inside a function, you cannot directly call them through the variable name, because the function has its own independent scope. At this time, you need to use the global keyword or $GLOBALS hyperglobal array to achieve it.
Access global variables using global keywords
This is the most common way. You just need to use global to declare the global variable you want to use.
$var = "Hello World";
function demo() {
global $var;
echo $var;
}
demo(); // Output: Hello World This method is suitable for situations where there are not many variables. But it should be noted that if multiple global variables are declared in the function, global must be added one by one.
- Advantages: The grammar is simple, intuitive and easy to understand.
- Disadvantages: It is easy to cause variable pollution and affect the maintainability of the code.
Use $GLOBALS hyperglobal array
PHP provides a hyperglobal array $GLOBALS that contains all global scoped variables in the current script.
$var = "Hello World";
function demo() {
echo $GLOBALS['var'];
}
demo(); // Output: Hello WorldThis method does not require declaring variables in advance, but is accessed directly through the array index.
- Advantages: No additional declaration is required, suitable for accessing multiple global variables.
- Disadvantages: The writing method is a bit cumbersome and the readability is slightly poor.
Notes and suggestions
- Avoid abuse : Frequent use of global variables will make the code difficult to debug and maintain, and try to control the scope of use.
- Naming conflict problem : Global variables are prone to conflict with other code segments, especially in large projects.
- Alternative : You can consider passing variables into functions as parameters, or encapsulating data using classes and static properties.
Basically these methods are all. Although they are not complicated, you should pay special attention to the rationality of the variable scope and code structure when using them.
The above is the detailed content of How to access a global variable inside a PHP function?. For more information, please follow other related articles on the PHP Chinese website!
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