Main article: PHP syntax and semantics
The following Hello world program is written in PHP code embedded in an HTML document:However as PHP does not need to be embedded in HTML, or used with a web server, the simplest version of a Hello World program can be written like this:<!DOCTYPE html> <meta charset="utf-8"> <title>PHP Test</title> <?php echo 'Hello World'; ?>
<?= 'Hello world';
<?php to open and ?> to close PHP sections. <script language="php"> and </script> delimiters are also available, as are the shortened forms <? or <?= (which is used to echo back a string or variable) and ?> as well as ASP-style short forms <% or <%= and %>. While short delimiters are used, they make script files less portable as support for them can be disabled in the PHP configuration, and so they are discouraged.[37] The purpose of all these delimiters is to separate PHP code from non-PHP code, including HTML.[38]The first form of delimiters,
<?php and ?>, in XHTML and other XML documents, creates correctly formed XML 'processing instructions'.[39] This means that the resulting mixture of PHP code and other markup in the server-side file is itself well-formed XML.Variables are prefixed with a dollar symbol, and a type does not need to be specified in advance. Unlike function and class names, variable names are case sensitive. Both double-quoted (
"") and heredoc strings provide the ability to interpolate a variable's value into the string.[40] PHP treats newlines as whitespace in the manner of a free-form language (except when inside string quotes), and statements are terminated by a semicolon.[41] PHP has three types of comment syntax: /* */ marks block and inline comments; // as well as # are used for one-line comments.[42] The echo statement is one of several facilities PHP provides to output text, e.g., to a web browser.In terms of keywords and language syntax, PHP is similar to most high level languages that follow the C style syntax.
if conditions, for and while loops, and function returns are similar in syntax to languages such as C, C++, C#, Java and Perl.
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