User Define Function in PHP

using this we can create our own function and manage program code in a Structured pattern.

PHP provides two different types of user-defined functions.

if we create 1000 lines of code in the PHP file then it is not understandable for other developers hence we create a function to subdivided the program code into multiple parts which can be easily understandable and reusable.

If we have common code in the project then that code can be placed under the function block and reused into multiple files.

1) Default:-  We can not pass value from calling function to called function.

function addition()
{
   }
1.1)  With return type:-  We can return value from calling function to called function.

function functionname()

{

     return output;

}
1.2) Without return type:-  We can not return value from calling function to called function all functionality will be defined under the function block.

function funtionname()

{

      Statements;

}

Example of Default function:-

<?php

function add()

{

  $a=10;

  $b=20;

  echo $a+$b;

}

function sub()

{ $a=100;

$b=20;

return $a-$b;

}

add();

$res = sub();

echo "<br>".$res;

?>

2) Parametrized:-  We can pass value from calling function to called function
function addition($x,$y)
{
      echo $x+$y;
}
Example of parametrized:-

<?php

function add($a,$b)

{ 

  echo $a+$b;

}

function sub($a,$b)

{

return $a-$b;

}

$x=100;

$y=200;

add($x,$y);

$res = sub(20,2);

echo "<br>".$res;

?>

Example of default and parametrized Function in PHP:-
<?php
  function addition($x,$y)  //param
  {
  echo $x+$y."<br>";
  }
   function sub()   //default
  {
  $x=100;
  $y=20;
  echo $x-$y."<br>";
  }

addition(100,20);  //calling
addition(1000,200);
sub();  //calling
sub();
?>

What is the global keyword in function?

It is used to declare a global variable in a function that can be used in another function.

function add($a,$b)

{

  global $x;   //scope is global means we can use into another function block

  $x=100;

  echo $a+$b;

}

function sub($a,$b)

{

    global $x; 

   

echo $x;

return $a-$b;

}