When PHP processes a file, it recognizes the opening and closing
tags, <?php and ?>, to
define the boundaries of PHP code execution. Content outside these
tags is ignored by the PHP parser, allowing PHP to seamlessly embed
in various document types.
A whitespace character (space, tab, or newline) must follow
<?php to ensure proper token separation.
Omitting this whitespace will result in a syntax error.
PHP also includes the short echo tag <?=,
which is shorthand for <?php echo.
Example #1 PHP Opening and Closing Tags
1. <?php echo 'if you want to serve PHP code in XHTML or XML documents, use these tags'; ?>
2. You can use the short echo tag to <?= 'print this string' ?>. It's equivalent to <?php echo 'print this string' ?>.
3. <? echo 'this code is within short tags, but will only work '. 'if short_open_tag is enabled'; ?>
Short tags (example three) are available by default but can be disabled
either via the short_open_tagphp.ini configuration file directive, or are disabled by default if
PHP is built with the --disable-short-tags configuration.
Note:
As short tags can be disabled it is recommended to only use the normal
tags (<?php ?> and <?= ?>) to
maximise compatibility.
If a file contains only PHP code, it is preferable to omit the PHP closing tag
at the end of the file. This prevents accidental whitespace or new lines
being added after the PHP closing tag, which may cause unwanted effects
because PHP will start output buffering when there is no intention from
the programmer to send any output at that point in the script.
