"<<<" in php

tkm · January 4, 2008

Hello,

Can anyone pls tell me what is "<<<" used for in PHP? The code I have with me uses "<<<" to assign a javascript block to a php variable. I think it is a very novice question but a reply would really help. I have searched in google but couldn't find anything related.

Thank you.

wildteen88 · January 4, 2008

DO you mean code which looks like this:

echo <<<EOF

big block of output here

EOF;

If so that is called a HEREDOC statement.

p2grace · January 4, 2008

You use it to create strings with many quotes without having to escape each quote.

Example:

echo <<<HTML
<a href="test.php">I'm using multiple "quotations" with $variables inside.
HTML;

awpti · January 4, 2008

NOTE:

HEREDOC is very inefficient. Avoid using it.

sKunKbad · January 4, 2008

NOTE:

HEREDOC is very inefficient. Avoid using it.

I'm not saying your wrong, but why do you say that?

mrdamien · January 5, 2008

NOTE:

HEREDOC is very inefficient. Avoid using it.

I'm not saying your wrong, but why do you say that?

Yeah, explain please.

There is a benchmark on the HEREDOC. The numbers point to heredoc being faster with string replacement.

test_double_quote_replace : 147ms

test_eot_replace : 130ms

p2grace · January 5, 2008

I agree, I use HEREDOC all the time and I've never had a problem with it.

awpti · January 5, 2008

They are more intensive for PHP to parse than single or double-quoted strings, resulting in slower code execution and increased memory usage (memory usage part isn't always noticable).

http://www.awpti.org/test_heredoc/ - >Result: ~0.178 -> 0.233

http://www.awpti.org/test_heredoc/double_quote/ - >Result: ~ 0.133 -> 0.145

Take into consideration that this test was built using the CodeIgniter Benchmark class/Framework.

The actual times on this will be lower, but double_quote is still faster.

Load the page and scroll to the bottom.

And the code..

<?php
class Test_heredoc extends Controller {

        function Test_heredoc()
        {
                parent::Controller();
        }

        function index()
        {
                $this->benchmark->mark('code_start');
                $tests = 10000;
                for($i=0;$i<$tests;++$i)
                {
                        $string = 'blah-'.$i;
echo <<<EOF
This is a test $string. This should run 10000 times.<br />
EOF;
                }
                $this->benchmark->mark('code_end');
                echo 'Time taken: '.$this->benchmark->elapsed_time('code_start', 'code_end').'<br />';
                $this->view->load('test/mem');
        }

        function double_quote()
        {
                $this->benchmark->mark('code_start');
                $tests = 10000;
                for($i=0;$i<$tests;++$i)
                {
                        $string = 'blah-'.$i;
                        echo "This is a string with $string in it.<br />";
                }
                $this->benchmark->mark('code_end');
                echo 'Time taken: '.$this->benchmark->elapsed_time('code_start', 'code_end').'<br />';
                $this->view->load('test/mem');
        }
}
?>

In retrospect, I should have named this test_perf

sKunKbad · January 5, 2008

When I ran your tests just now, there was a four tenths of a second difference, and memory usage was the exact same. I think it is VERY unlikely that the difference is great enough to effect the user's experience of any of my pages. While I do agree there your tests prove that heredoc is slower than double quotes when looped 10000 times, in the case of normal usage the difference is probably indistinguishable. Let's not quibble over such a minute amount of time! Saying , "heredoc is very inefficient. Avoid using it.", is a bit of an exaggeration.

mrdamien · January 5, 2008

Interesting result but I couldn't help notice how the HEREDOC test uses a longer string. Could you do the same test but with both strings exactly the same?

echo <<<EOF

This is a test . This should run 10000 times.<br />

EOF;

$string = 'blah-'.$i;

echo "This is a string with in it.<br />";

awpti · January 5, 2008

I shrunk the string, now they're both about the same. I didn't think about it earlier, but these results may be poisoned by the fact my hosting server is a Virtual instance among a few others. They both swing pretty big in the results - ranging from 0.3x to 0.9x+

I'll actually be shifting off to a dedicated server soon - be able to do a more reliable test then.

As far as the difference being minor?

Any savings is a saving. I'll also assume you ment 4 hundredths and not 4 tenths. 4 tenths would be a significant savings (and an odd result ).

It may be a -slight- exaggeration to say 'very' on short HEREDOC's.. start pumping out serious content w/ variables using HEREDOC and you'll feel the hurt when the site gets active. I had to deal with a site that did such a thing and it was AWFUL. The performance was horrible and the memory usage difference was visible (still insignificant compared to the processing time).

Every page was, pretty much, a HEREDOC with about 30-40 variables being dumped to it, with breaks out of the HEREDOC to take care of 'for' loops.

Start running load tests. You'll see load times/processing times increase exponentially. Every little tweak matters when your site is live and high-traffic. That .04 can be the difference between crushing your server's CPU or not during a spike.

hitman6003 · January 5, 2008

For comparison, here is the code and results I used / got:

function microtime_float() {
    list($usec, $sec) = explode(" ", microtime());
    return ((float)$usec + (float)$sec);
}

$heredoc_times = array();
$echo_times = array();

for ($i = 0; $i < 10000; $i++) {
$start = microtime_float();

echo <<<LINE

test test test $start test test test

LINE;

$heredoc_times[] = (microtime_float() - $start);

}

for ($i = 0; $i < 10000; $i++) {
$start = microtime_float();

echo "

test test test $start test test test

";

$echo_times[] = (microtime_float() - $start);

}

echo '<pre>
HEREDOC:
Total: 		' . array_sum($heredoc_times) . '
Average:	' . (array_sum($heredoc_times) / count($heredoc_times)) . '

echo:
Total: 		' . array_sum($echo_times) . '
Average:	' . (array_sum($echo_times) / count($echo_times));

HEREDOC:
Total: 		0.210633277893
Average:	2.10633277893E-5

echo:
Total: 		0.221266508102
Average:	2.21266508102E-5

I'm using a Core2 Duo Laptop with 2 GB RAM running the latest version of XAMPP (PHP 5.2.5, Apache 2.2.6).

awpti · January 5, 2008

Seems like everyone is getting different results.

At the console (php test.php)

HEREDOC:

Total: 0.28366875648499

Average: 2.8366875648499E-5

echo:

Total: 0.22118401527405

Average: 2.2118401527405E-5

Via apache (2.2.6 w/ php 5.2.5):

HEREDOC:

Total: 0.28366875648499

Average: 2.8366875648499E-5

echo:

Total: 0.22118401527405

Average: 2.2118401527405E-5

???

tkm · January 5, 2008

Hello Everyone,

Thank you. Great stuff. I wasn't expecting such quick response...and yes the code I am working on is using "<<<" as "Heredoc". Thank you guys again....love php freaks forum...

mrdamien · January 5, 2008

1.5ghz cpu

apache 2.2.6

php 4

HEREDOC:
Total: 0.538983345032

Average: 5.38983345032E-5

echo:

Total: 0.798581123352

Average: 7.98581123352E-5

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"<<<" in php

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