What are local variables and global variables in php

Variables are containers for storing information:

#1. Global variables defined outside the function have their scope from definition until the end of the file.

2. The variables defined within the function are local variables, and their scope is within the function definition scope.

3. There are scopes between functions that do not affect each other. (Recommended learning: PHP programming from entry to proficiency)

4. Accessing global variables within a function requires the global keyword or the $GLOBALS[index] array

in php The function has an independent scope, so local variables will overwrite global variables. Even if the local variables do not have the same variables as global variables, they will be overwritten. As follows:

<?php
$a=5;
$b=3;
function t()
{
    echo $a-$b; // 输出 0
}
t();
?>

If you want to use global variables directly in the function, you can declare it through the global keyword or obtain it through the custom $GLOBALS array in php:

<?php
$a=5;
$b=3;
function t1()
{  
    global $a,$b;
    echo $a-$b;  // 输出 2
}
t1();

echo PHP_EOL;

function t2()
{
    echo $GLOBALS[&#39;a&#39;]-$GLOBALS[&#39;b&#39;];  // 输出 2
}
t2();
?>

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