PHP Comments, String Concatenation, Addition of Numbers & Hello World

Today lets see these 4 basic things:
1. The classic “Hello World” program.
2. Comment system in PHP.
3. Concatenation of Strings.
4. Addition of Numbers.

Classic “Hello World” program
Program to output simple string

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<?php
          echo "Hello World";
?>

Comments:

1

// This is single line comment

1

# This is also a single line comment

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/* This is how multi-line comments
    are written.
*/

Anything following a double forward slash or a hash( # ) symbol will be ignored by your parser. Comments are very important and are often ignored by programmers. Comments come handy when we come back to the codes and want to make some changes to the coding. So its always a good practice to write comments wherever appropriate.

Concatenation of Strings
Concatination is joining of two or more strings end to end. Ex: if we concatenate Micro and soft, it will become Microsoft.
In PHP, we use .[DOT] operator for concatenation. Below is an example:

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<?php 
         echo "Micro" . "soft";
         echo "<br />Oracle, " . "Sun Microsystems";
?>

The output for the above php code is:

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Microsoft
Oracle, Sun Microsystems

Addition of Numbers
We can use variables for addition of numbers or we can simply make use of echo or print for addition of numbers.

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<?php
         echo 10+20;
?>

This gives 30 as the output.

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<?php
         echo "5"+10;
?>

This gives 15 as output. The string “5” will be implicitly converted into number and will be added to the actual number 10.