What are the considerations for passing variables to functions in PHP, especially when dealing with global variables?

When passing variables to functions in PHP, especially when dealing with global variables, it's important to consider whether to pass variables by reference or by value. Passing variables by reference allows the function to directly modify the original variable, while passing by value creates a copy of the variable within the function. To pass global variables to a function, you can use the global keyword within the function to access the global variable directly. 

// Passing global variable by reference
$globalVar = 10;

function modifyGlobalVar(&$var) {
    $var *= 2;
}

modifyGlobalVar($globalVar);
echo $globalVar; // Output: 20

// Accessing global variable within a function
$globalVar2 = 5;

function accessGlobalVar() {
    global $globalVar2;
    echo $globalVar2;
}

accessGlobalVar(); // Output: 5

Keywords

global variables function parameters scope pass by reference variable passing

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