Post-3 (PHP) Declare Variables in PHP - NetwaxUL

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Saturday, March 26, 2016

Post-3 (PHP) Declare Variables in PHP

# Creating (Declaring) Variables in PHP


  • Example: 7

<?php

$txt = "Hi Netwax Lab!";

$x = 5;

$y = 10.5;
echo $txt;
echo "<br>";
echo $x;
echo "<br>";
echo $y;
?>

Output

Hi Netwax Lab!
5
10.5

# How to Output Text and a Variable

  • Example: 8
<?php
$txt = "Hi Netwax Lab!";
echo "Hey $txt!";
?>

Output

Hey Hi Netwax Lab!!

  • Example: 9
<?php
$txt = "Hi Netwax Lab!";
echo "Hey " . $txt . "!"
?>

Output

Hey Hi Netwax Lab!!
  • Example: 10
<?php
$a = 10;
$b = 15;
echo $a+$b;
?>

Output

25

PHP has three different variable scopes:
  1. Local
  2. Global
  3. Static

# Global and Local Scope

Define variable global still not use in inside function
  • Example: 11
<?php
$a = 10; // variable global scope
function First() {
// using a inside this function will generate an error
echo "<p>Variable a inside function is: $a</p>";
}
First();
echo "<p>Variable a outside function is: $a</p>";
?>

Output


  • Example: 12
<?php
function First() {
$a = 10; // variable local scope
// using a outside this function will generate an error
echo "<p>Variable a inside function is: $a</p>";
}
First();
echo "<p>Variable a outside function is: $a</p>";
?>

Output


  • Example: 13
<?php
$a = 10; // variable global scope
function First() {
global $a;
echo "<p>Variable an inside function is: $a</p>";
}
First();
echo "<p>Variable an outside function is: $a</p>";
?>
<?php
$a = 10; // variable global scope
function First() {
global $a;
echo "<p>Variable an inside function is: $a</p>";
}
First();
echo "<p>Variable an outside function is: $a</p>";
?>

Output

Variable an inside function is: 10
Variable an outside function is: 10

PHP also stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable.

This array is also accessible from within functions and can be used to update global variables directly.
  • Example: 14
<?php
$a = 10; // variable global scope
function First() {
$GLOBALS['a'] = $GLOBALS['a'] + $GLOBALS['a'];
}
First();
echo "<p>Variable an outside function is: $a</p>";
?>

Output

Variable an outside function is: 20

# Static Keyword

When a function is completed/executed, all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job.
  • Example: 15
<?php
function First() {
static $a = 0;
echo $a.'<br>';
$a++;
}
First();
First();
First();
?>

Output

0
1
2



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