function in php like control loop and its uses

What is a Function in PHP
• A Function in PHP is a reusable piece or block of code that
performs a specific action.

Create a User Defined Function in PHP
A user-defined function declaration starts with the word function:

PHP User Defined Functions
Besides the built-in PHP functions, it is possible to create your own functions.
•A function is a block of statements that can be used repeatedly in a
program.
•A function will not execute automatically when a page loads.
•A function will be executed by a call to the function.

Why use Functions?
•Better code organization – PHP functions allow us to group blocks of
related code that perform a specific task together.
•Reusability – once defined, a function can be called by a number of scripts
in our PHP files. This saves us time of reinventing the wheel when we want
to perform some routine tasks such as connecting to the database
•Easy maintenance- updates to the system only need to be made in one
place.

<?php
function hello()
{
echo" hello everybody";
}
hello();
hello();
echo" hi hw r u";
hello();
?>

Advantage of PHP Functions
Code Reusability: PHP functions are defined only once and can be invoked
many times, like in other programming languages.
Less Code: It saves a lot of code because you don't need to write the logic
many times. By the use of function, you can write the logic only once and
reuse it.
Easy to understand: PHP functions separate the programming logic. So it
is easier to understand the flow of the application because every logic is
divided in the form of functions.

PHP Function Arguments
• Information can be passed to functions through arguments. An
argument is just like a variable.
• Arguments are specified after the function name, inside the
parentheses. You can add as many arguments as you want, just
separate them with a comma.

<?php
function hello($name,$lname)
{
echo"hello $name,$lname. ";
}
hello(“Anil","kumar");
hello(“Ajay",“Sharma");
?>

Write a function to calculate the factorial of a number (a non-negative
integer). The function accepts the number as an argument.

<?php
function
factorial_of_a_number($n)
{
if($n ==0)
{
return 1;
}
else
{
return $n *
factorial_of_a_number($n-1);
}
}
print_r(factorial_of_a_number(4)
."n");
?>

<!DOCTYPE html>
<html>
<body>
<?php
function familyName($fname, $year) {
echo "$fname Refsnes. Born in $year ";
}
familyName("Hege","1975");
familyName("Stale","1978");
familyName("Kai Jim","1983");
?>
</body>
</html>

PHP strict typing
• In this example, the add() function
accepts two integers and returns the
sum of them.
• However, when you pass two floats
1.5 and 2.5, the add() function
returns 3 because PHP implicitly
coerces the values to the target types
by default.
• In this case, PHP coerces the floats
into integers.
• To enable strict typing, you can use
the declare (strict_types=1); directive
at the beginning of the file.

• To enable strict typing, you can use the declare(strict_types=1);
• By adding the strict typing directive to the file, the code will
execute in the strict mode. PHP enables the strict mode on a
per-file basis.
• In the strict mode, PHP expects the values with the type
matching with the target types. If there’s a mismatch, PHP will
issue an error.

<?php
Function hello($name="first",$lname="last")
{
Echo "hello $name,$lname. ";
}
hello("deepinder");
hello(“kiran",“deep");
?>

<?php
function hello($name="first",
$lname="last")
{
echo"hello $name,$lname. ";
}
function sum($a,$b)
{
echo $a+$b;
}
hello("deepinder");
hello("renu","dhiman");
sum(10,20);
?>

<?php
function add($n1=10,$n2=10)
{
$n3=$n1+$n2;
echo "Addition is: $n3 ";
}
add();
add(20);
add(40,40);
?>

Parameter passing to Functions
PHP allows us two ways in which an argument can be passed into a function:
•Pass by Value: On passing arguments using pass by value, the value of the
argument gets changed within a function, but the original value outside the
function remains unchanged. That means a duplicate of the original value is
passed as an argument.
•Pass by Reference: On passing arguments as pass by reference, the original
value is passed. Therefore, the original value gets altered. In pass by reference we
actually pass the address of the value, where it is stored using ampersand
sign(&).

<?php
function
testing($string)
{
$string.="hello";
}
$str="this is string";
testing($str);
echo $str;
?>
Call by Value

<?php
function testing(&$string)
{
$string.="hello";
}
$str="this is string";
testing($str);
echo $str;
?>
Call by Reference

<!DOCTYPE html>
<html>
<body>
<?php function adder(&$x)
{
$x .= ' This is Call By Reference ';
}
$y = 'Hello PHP.';
adder($y); echo $y;
?>
</body>
</html>

<!DOCTYPE html>
<html>
<body>
<?php
function incre(&$i)
{
$i++;
}
$i = 1;
incre($i);
echo $i;
?>
</body>
</html>
OUTPUT
?

CALL BY VALUE
<!DOCTYPE html>
<html>
<body>
<?php function adder($x)
{
$x .= 'Call By Value';
}
$y = 'Hello PHP';
adder($y);
echo $y;
?>
</body>
</html>

<!DOCTYPE html>
<html>
<body>
<?php
function incre($i)
{
$i++;
}
$i = 1;
incre($i);
echo $i;
?>
</body>
</html>
OUTPUT
?

<?php
function display($number)
{
if($number<=5)
{
echo "$number ";
display($number + 1);
}
}
display(1);
?>

PHP Default Parameters
• The following defines the concat() function that concatenates two strings
with a delimiter:

• -PHP allows you to specify a default argument for a parameter.
For example:
• In this example, the $delimiter parameter takes the space as
the default argument.

PHP Anonymous Functions
• When you define a function, you specify a name for it. Later, you can call the
function by its name.
• For example, to define a function that multiplies two numbers, you
can do it as follows:

• An anonymous function is a function that doesn’t have a name.
• The following example defines an anonymous function that
multiplies two numbers:

1. Code to generate factorial of a number using recursive function in PHP.
TRY THIS
2. Write a program to print numbers from 10 to 1 using the
recursion function.

function in php like control loop and its uses

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