Mike Cochrane

[PHP] On Copyright Year

2007-10-08T05:13:31-07:00

@JWvdV: Close, but you missed the ' - ' between then years. And the syntax error.

<?php
echo "Copyright &copy; 2007" . ((intval(date('Y')) != 2007) ? date(' - Y') : '') . " - All Rights Reserved - Design by scott2010_h";
?>

[PHP] On Bytes to Readable

2007-10-08T05:07:05-07:00

> Make this simpler?

No, I can't make it simpler (from a human point of view) but I can make it faster.

[PHP] On Bytes to Readable

2007-10-08T02:17:03-07:00

Okay, there was a bug in my rounding code. Here's the corrected version. Completes in 51% of the time of the original.

<?php
function getsize($size) {
    $si = array('B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB');
    $remainder = $i = 0;
    while ($size >= 1024 && $i < 8) {
        $remainder = (($size & 0x3ff) + $remainder) / 1024;
        $size = $size >> 10;
        $i++;
    }
    return round($size + $remainder, 2) . ' ' . $si[$i];
}

[PHP] On Bytes to Readable

2007-10-08T01:52:53-07:00

My code does everything with bit shifts. Also doesn't output a divide by zero error when size = 0. In my trials it completes in 49% of the time of the original. My code is not 100% equivalent - when size = 0 my code returns '0 B', the original returns '0 '.

function getsize($size) {
    $si = array('B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB');
    $remainder = $i = 0;
    while ($size >= 1024 && $i < 8) {
        $remainder = $size & 0x3ff;
        $size = $size >> 10;
        $i++;
    }
    return round($size + ($remainder/1024), 2) . ' ' . $si[$i];
}

[PHP] On ISBN10 to ISBN13

2007-10-03T17:25:58-07:00

Thanks James. You're right on the ISBN-10 check sum range. For ISBN-13 is ranges from 0-9. There is no A according to http://www.isbn-international.org/ or Wikipedia. Thanks for pointing this out.

So my previous solution was incorrect. Here is a correct solution. Performance hit in the fix though.

So final result is 45% time saving on leightmac's but it doesn't reject legit numbers and the check digit is always a single digit, not '10' like it could have previously been.

function isbn10_to_13($isbn) {
    if (!preg_match('{^([0-9]{9})[0-9xX]$}', $isbn, $matches)) {
        # number is not 10 digits
        return false;
    }

    # sum the digits with their weights and add the checksum for the 978 prefix
    $sum_of_digits = 38 + 3 * ($isbn{0} + $isbn{2} + $isbn{4} + $isbn{6} + $isbn{8}) +
                               $isbn{1} + $isbn{3} + $isbn{5} + $isbn{7};

    # divide the sum_of_digits by the modulus number (10) to find the remainder
    # and then minus 10 to get the check digit
    $check_digit = (10 - ($sum_of_digits % 10)) % 10;

    # return isbn with check_digit
    return '978' . $matches[1] . $check_digit;
}

[PHP] On Content Page Include

2007-10-03T03:45:00-07:00

I did a quick performance test. Using the two functions below - eliminating the file operations and returning the string instead. Run once timed, change function, timed, changed back, timed, changed to v2 again, timed.
For two pages, the switch took 49.9% of the time of my code - switch wins by heaps (15,000 calls - two runs avg of both).
For 101 pages, the switch took 49.5% of the time of my code - (255,000 calls - one run each)

So there you have it. The switch is twice as fast as my code. Take your pick :-)

FYI in 101 page test:
v3 was 107% of v2 (the ternary construct is faster in this case).
v4 was 52% of v2 (in_array is the killer in v2).
v5 was identical to v2 (v2 with array_search($_GET['id'], $pages) !== false instead of in_array)

### Test one
function v1() {
    switch($_GET['id'])
    {
       default:
       case "news":
          return "news.php";
       break;

       case "about":
          return "about.php";
       break;
    }
}

function v2() {
    $pages = array('news', 'about');
    return (isset($_GET['id']) && in_array($_GET['id'], $pages)) ? $_GET['id'] . '.php' : 'default.php';
}

$_GET['id'] = 'news';
for ($i = 0; $i < 5000; $i++) v1();
$_GET['id'] = 'about';
for ($i = 0; $i < 5000; $i++) v1();
$_GET['id'] = '';
for ($i = 0; $i < 5000; $i++) v1();

### Test 2
function v1() {
    switch($_GET['id'])
    {
       default:
       case "news":
          return "news.php";
       break;

       case "page1":
          return "page1.php";
       break;

       case "page2":
          return "page2.php";
       break;

...

       case "page99":
          return "page99.php";
       break;

       case "about":
          return "about.php";
       break;
    }
}

function v2() {
    $pages = array('news', 'page1', 'page2', .... 'page99', 'about');
    return (isset($_GET['id']) && in_array($_GET['id'], $pages)) ? $_GET['id'] . '.php' : 'default.php';
}

function v3() {
    $pages = array('news', 'page1', 'page2', .... 'page99', 'about');
    if (isset($_GET['id']) && in_array($_GET['id'], $pages)) {
        return  $_GET['id'] . '.php';
    } else {
        return 'default.php';
    }
}

function v4() {
    if (!isset($_GET['id'])) {
        return "news.php";
    }
    switch($_GET['id'])
    {
       default:
       case "news":
          return "news.php";
       break;

       case "page1":
          return "page1.php";
       break;

       case "page2":
          return "page2.php";
       break;

....

       case "page98":
          return "page98.php";
       break;

       case "page99":
          return "page99.php";
       break;

       case "about":
          return "about.php";
       break;
    }
}

function v5() {
    $pages = array('news', 'page1', 'page2',. ... 'page99', 'about');
    return (isset($_GET['id']) && array_search($_GET['id'], $pages) !== false) ? $_GET['id'] . '.php' : 'default.php';
}

$_GET['id'] = 'news';
for ($i = 0; $i < 2500; $i++) v1();
$_GET['id'] = 'about';
for ($i = 0; $i < 2500; $i++) v1();
$_GET['id'] = '';
for ($i = 0; $i < 2500; $i++) v1();

for ($p = 1; $p < 100; $p++) {
    $_GET['id'] = 'page' . $p;
    for ($i = 0; $i < 2500; $i++) v1();
}