Php function local variable declaring global

Use parameters before global state

PHP can access a global variable with global or $GLOBALS, but parameters and return values usually make dependencies clearer. Reserve global state for cases where it is genuinely part of the application's design.

<?php
function greeting(string $name): string {
    return 'Hello ' . $name;
}

echo greeting('Ravi');
?>

Design tip: Prefer parameters and return values over global state when practical; they make the function dependency explicit.

Many times we will not get the value of the variables inside a function to use. The reason is that the variables became local inside the function so variables declared outside the function will not be available inside the function for use.
Also the variables used inside the function will not be available for the main script to use. For this return statement is to be used.

We can also pass the variables into the function by using arguments. To use the variables of main script inside the function we have to make them global first. Here is the code explaining how variables can be declared inside the function as global.

<?php
$v1="Hello 1";
function test(){
echo "The value of \$v1= $v1";
// The above line will print The value of $v1=
global $v1;
echo "<br>The value of \$v1= $v1";
// The above line will print The value of $v1= Hello 1
$v2="Hello 2";
}
test();

echo "<br>The value of \$v2=$v2";
// The above line will print The value of $v2= 
?>

In above code we have seen the local variable inside the function lost its value once function execution is completed. To retain the values for successive execution of the function we have to use static variables. Here is the code to explain about static variables.

<?php
function my_function(){
static $my_static_variable=0;
$my_local_variable=0;
$my_static_variable=$my_static_variable + 1 ;
$my_local_variable=$my_local_variable + 1 ;
echo "Static varaible :".$my_static_variable;
echo ",Local Variable :".$my_local_variable;
}

my_function();
echo "<br>";
my_function();
?>

Output is here.

Static varaible :1, Local Variable :1
Static varaible :2, Local Variable :1

The data associated with static variable is retained after the execution of the function.

Global Variables

We can declare variables inside or outside the function to make it available throughout the script.

$v1=2; 
$v2=6;
function test(){ 
$GLOBALS[v3]=$GLOBALS[v1]+$GLOBALS[v2];
} 
test(); 
echo $v3; // Output is 8

We can declare variables as Global outside the function.

$GLOBALS[v1]=2; 
function test(){ 
$v1=5; //  local variable 
} 
test(); 
echo $v1; // Output is 2 ( not 5 )

Functions Types of variables in PHP

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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Adam	25-06-2014
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Subhendu Mohapatra