* Php tags Short open tag (<? OR <?=) are enabled by default in php.ini (short_open_tag = on)
<?php if (ini_get('short_open_tag') == 1): ?> <? echo "Short open tag ENABLED"; ?> <?php endif; ?> Short tags <? ... ?> have the major drawback of conflicting with XML headers With <?php is working correctly (View Source: <?xml version="1.0" ?>)
<?php // --- Look Here -- // echo <<<EOF <?xml version="1.0" ?> EOF; ?> With <? is displaying EOF;
<? // --- Look Here -- // echo <<<EOF <?xml version="1.0" ?> // --- Look Here -- // EOF; ?> * Newline Characters It is good practice to ommit the closing php tag because newlines are used as separators between the header of HTTP server response and the actual data.
<?php // test.php $a = 1; ?> [newline] [newline]
<?php // index.php error_reporting(E_ALL); include('test.php'); header("HTTP/1.0 404 Not Found"); // Warning: Cannot modify header information - headers already sent by // Without [newline] will be ok // So it's good practice to omit closing tag Alternativly, you can use output_buffering flag in php.ini
; php.ini ; Output buffering allows you to send header lines (including cookies) even ; after you send body content, at the price of slowing PHP's output layer a bit. output_buffering = 4096 * Comments Single line comments can be ended using newline characters (r,n or rn) or by using PHP closing tag ?> Later can cause unintended output.
// don't show this ?> or this // will output "or this" Example of comments:
// Single line comment # Single line comment /** Multi-line comment */ /** API documentation example * * @param string $bar */ function foo($bar) {} * Code blocks
<?php // block code A { echo 1; } // block code B { echo 2; } * Language constructs Are elements that are built-into the language.
<?php $a = echo 4; // Parse error: syntax error, unexpected T_ECHO // echo does not have a return value $a = print(4); // output 4
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