Constants in PHP
Constants in PHP cannot be changed or made undefined once they have been defined. Similar to a variable in PHP is a constant. There are two methods to create constants in PHP.
- Using define() function
- Using const keyword
How to Create a PHP Constant
Using define() function:
To create a constant in PHP, we use the define() function.
Syntax
- name: It is considered the constant name.
- value: It is considered as the constant value.
- case-insensitive: It is considered whether a constant is case-insensitive.
Example
Let’s create a constant with a case-sensitive name:
<!DOCTYPE html>
<html>
<body>
<?php
// case-sensitive constant name
define("WELCOME", "Hello oraltadalafil.com!");
echo WELCOME;
?>
</body>
</html>
OUTPUT: Hello oraltadalafil.com!Let’s create a constant with a case-insensitive name:
Example
<!DOCTYPE html>
<html>
<body>
<?php
// case-insensitive constant name
define("WELCOME", "Hello oraltadalafil.com!", true);
echo welcome;
?>
</body>
</html>
OUTPUT: oraltadalafil.com!PHP Constant Arrays
In PHP7, by using the define() function we can create an Array constant.
Example
<!DOCTYPE html>
<html>
<body>
<?php
define("fruits", [
"apple",
"orange",
"mango"
]);
echo fruits[0];
?>
</body>
</html>
OUTPUT:
appleUsing const keyword:
In PHP, a constant is made using the keyword const. Constants are defined during compilation by the keyword const. Case matters when defining constants with the const keywords.
Example
<?php const MESSAGE="Hello const by oraltadalafil PHP"; echo MESSAGE; ?>
OUTPUT: Hello const by oraltadalafil PHPConstant() function in PHP
Instead of using the echo statement, we can also print the value of constants using the constant() function.
Syntax : constant (name)
<?php
define("MSG", "oraltadalafil");
echo MSG, "</br>";
echo constant("MSG");
//both are similar
?>
OUTPUT:
oraltadalafil
oraltadalafilDifference between Constant and Variables
| Constant | Variable |
| A constant can be defined by using the define() function. Any simple task cannot describe it. | A variable can be undefined and as well as it can be redefined easily. |
| Once the constant is defined, then it can’t be redefined. | An assignment (=) operator is used to define the variable in PHP. |
| Constants are those variables whose values can’t be modified throughout the program. | To declare a variable, we use the dollar ($) sign before the variable. |
| There is no need for a dollar ($) sign before constant during the assignment. | Variables can be expressed anywhere in the program, but they follow variable scoping rules. |
| By default, constants are global. | The value within the variable can be changed. |
| A constant can be defined and accessed anywhere. | In PHP, variables can be local, global, or static. |
PHP Strings
A string is called a sequence of characters, like “Hello world!”
PHP String Functions
There are some String functions that are used to manipulate the data.
· strlen() :
In PHP the strlen() returns the length of a string.
<!DOCTYPE html>
<html>
<body>
<?php
echo strlen("Hello world!");
?>
</body>
</html>
OUTPUT: 1str_word_count() :
In PHP the str_word_count() function counts the number of words in a string.
<?php
echo str_word_count("Hello world!");
?>
OUTPUT: 2strrev() :
In PHP the strrev() function is used to reverse the string.
<?php
echo strrev("Hello world!");
?>
OUTPUT: !dlrow olleHstrpos() :
The strpos() function searches for specific text which is within a string.
<?php
echo strpos("Hello world!", "world");
?>
OUTPUT: 6str_replace() :
The str_replace() function replaces some characters with some other characters in the string.
<?php
echo str_replace("Hero", "Honda", "Hero Honda!");
?>
OUTPUT:Honda Honda!
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