Scripts

• A file containing PHP code should ordinarily have an extension of .php

Shebang

• The first line must be one of the following, to indicate that the file is a PHP script:

• #!/usr/bin/php
• #!/usr/local/bin/php
• #!/usr/bin/env php
  

• The shebang is required for running PHP files as CGI scripts
• There's some controversy over which of the above approaches is best
• To find out which location PHP is run from on a given computer, type "which php"

PHP tags

<?php PHP_CODE ?>

• The preferred method
• Allows the use of PHP in XML-conformant code such as XHTML

<? PHP_CODE ?>

• Not always available
• <?= expression ?>  # Shortcut version to echo an expression

<script language="php"> PHP_CODE </script>

<% PHP_CODE %>

• Only available if ASP-style tags have been enabled
• <%= $variable; %>  # Shortcut version to echo a variable
  

Usage

• The closing tag automatically implies a semicolon; the last line of a PHP block does not have to be explictly terminated with a semicolon.
• The closing tag eats the end-of-line character that follows it.

Examples

<?php echo("text\n"); ?>
                        

<? echo ("text\n"); ?>
<?= "text\n" ?>

<script language="php"> echo ("text\n"); </script>
                        

<% echo ("text\n"); %>
<%= $variable; %>

Embedding PHP in html

• The PHP parser only executes code that's within PHP tags; the rest of the file is left as-is.

<?php
if ($expression) { 
?>
    <strong>This is true.</strong>
<?php 
} else { 
?>
    <strong>This is false.</strong>
<?php 
}
?>