Global keyword usage in PHP

PHP global keyword

The global keyword is used to access global variables within a function.

Example 1

$x=5;
$y=10;
function myTest() {  
    global $x,$y;//通过global来声明$x,$y，相当于传递参数
    $y=$x+$y;
}
  myTest();
echo $y;

Output

// 输出 15

Indicates that the values ​​of $x and $y defined outside the function have been referenced, and the values ​​within the function The sum is assigned to $y, and the sum calculated inside the function can also be obtained outside the function.

Global variables: variables outside the function, variables inside the function, and the superglobal variable of $GLOBAL.

The role of Global is to define global variables, but this global variable does not apply to the entire website, but to the current page, including all files in include or require.

But global variables defined within the function body can be used within the function body, while global variables defined outside the function body cannot be used within the function body. See the example below for details.

Note:

The reason is that you cannot assign a value to a variable while declaring it with global.

Define global variables within the function body, which can be used within the function body.

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