< Php Tutorial

Php syntax

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A PHP script is executed on the server, and the plain HTML result is sent back to the browser.

Basic PHP Syntax

A PHP script can be placed anywhere in the document. A PHP script starts with <?php and ends with ?>:

<?php 
  // PHP code goes here 
?>

The default file extension for PHP files is ".php". A PHP file normally contains HTML tags, and some PHP scripting code. Below, we have an example of a simple PHP file, with a PHP script that uses a built-in PHP function "echo" to output the text "Hello World!" on a web page:

Example

<html> 
<body>
   <h1>My first PHP page</h1>
   <?php echo "Hello World!"; ?> 
</body> 
</html>

Comments in PHP

A comment in PHP code is a line that is not read/executed as part of the program. Its only purpose is to be read by someone who is looking at the code. Comments can be used to:

  • Help others to understand your code.
  • When you re-visit the code, comment will help you understand the flow. Comments can remind you of what you were thinking when you wrote the code

PHP supports several ways of commenting:

Example

<html> 
<body>
<?php 
   // This is a single-line comment
   # This is also a single-line comment 
   /* This is a multiple-lines comment block that spans over multiple lines */ 
?> 
</body> 
</html>

PHP Case Sensitivity

1. In PHP, all keywords (e.g. if, else, while, echo, etc.), classes, functions, and user-defined functions are NOT case-sensitive.

In the example below, all three echo statements below are legal (and equal):

Example

<html> 
<body>
  <?php 
    echo "Hello World!<br>"; 
    Echo "Hello World!<br>"; 
    ECHO "Hello World!<br>"; 
  ?>
</body>
</html>

2. However all variable names are case-sensitive.

In the example below, only the first statement will display the value of the $color variable
(this is because $color, $COLOR, and $coLOR are treated as three different variables):

Example

<html> 
<body>
 <?php 
     $color = "red"; 
     echo "My car is " . $color . "<br>"; 
     echo "My house is " . $COLOR . "<br>"; 
     echo "My boat is " . $coLOR . "<br>"; 
 ?>
</body>
</html>
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