Category Archives: Software Development

Now that the basics have been covered in the previous two posts, I’ll continue with some thing a bit more useful… writing some logic.

Conditional Statements

In PHP the conditional operators are pretty much the same as in C#, however there are some subtle differences.

== and != use type coercion. That means that if the type on the left side is not the same as the type on the right side then PHP will coerce them so that they can be compared. For example:

$a = 1;
$b = 1.0;

if ($a == $b)
    echo 'a and b are equal.';
else
    echo 'a and b are not equal.';

It even works if one of them is a string representation of the number one.

To get the functionality you’d expect in C# you need to use === and !==.

There is also an additional not equals operator similar to == that consists of a left and right cheveron: <>

Be careful of accidentally using a single equal sign for comparison. In C# the compiler will issue an error if it doesn’t evaluate to a Boolean. However, in PHP everything can be evaluated as a Boolean (see the section on Booleans in my previous post).

You can join comparisons together with && or || just like in C#, however, PHP also supports the use of and or or.

if statements also support an elseif clause in PHP.

if ($a < 123)
{
    // Do stuff
}
elseif ($a == 123)
{
    // Do other stuff
}
else
{
    // Do different stuff
}

Unlike C#, switch statements allow one case clause to drop in to the next, so it does not require a break at the end of each case block. The break on the last case or default is not necessary either.

switch($a)
{
    case 1:
        // Do some stuff
        break;
    case 2:
        // Do stuff
    case 3:
        // Do stuff (and continue case 2 if necessary)
        break;
    default:
        // Do stuff for all other cases
        break;
}

Loops

PHP, like C#, has a number of loop statements depending on what you want to do.

for loops, while, and do … while work exactly the same way. So I won’t discuss them further.

Just like C#, you can break out of a loop, and continue to the next iteration of the loop.

In my previous post on PHP for ASP.NET Developers, I introduced the basics of how to set up a PHP environment and started showing the differences between PHP’s way of doing things from an ASP.NET developer’s perspective. In this post, I’m continuing with those differences.

Comments

Comments in PHP are very similar to C#. You can use /* to open a comment block and */ to close it later, and you can use the // format to comment to the end of a line.

PHP also allows the use of a hash symbol, #, to indicate that the remainder of the line is a comment.

Types

Booleans

In .NET a Boolean is a specific type and you had to get the type you are using into the Boolean to use it as such. In PHP things are a little more flexible. A Boolean can be true or false, as you might expect. But there are special cases with other types. For example, a string can be treaded as a Boolean (in an if statement, for example). If the string is empty or contains just “0” (zero) then it is treated a false. Any other value is true. Numbers have a similar effect. Zeros are treated as false and others are treated as true. null is also treated as false.

Dates

There are two ways to get the current date. The first is with a call to time() which returns a Unix timestamp (an integer representing the number of seconds between 00:00:00 on 1/1/1970 and the date in question). The other way is to use date() with just a format string which returns the current date formatted as specified. You can also call date and pass a timestamp and have it convert the timestamp in to the specified format. For example:

$nowTimestamp = time();
echo "<p>The time now is ".$nowTimestamp."</p>";

$nowDate = date('d/M/Y H:i:s');
echo "<p>The time now is ".$nowDate."</p>";

You can find the details of the formatting specifiers at php.net.

If you want to convert a specific date into a timestamp then you can use the function strtotime() to perform the conversion. It is quite powerful in ways that I didn’t expect, you can set the string to values such as “next Tuesday” and “yesterday”. However, the parsing of specific dates can be tricky. If you are using the American format which puts the month first you separate the components with a slash, if you are going for the European sequence which puts the day firsr then the month, you must use a dash as a separator.

For example:

$weddingTimestamp = strtotime('13-4-2012');
echo "<p>My wedding is ".$weddingTimestamp."</p>";

$weddingDate = date('d/M/Y', $weddingTimestamp);
echo "<p>My wedding is ".$weddingDate."</p>";

There is a DateTime class also available which can be used.

$now = new DateTime();
echo "<p>Today is ".$now->format('d-M-Y')."</p>";

Collections (arrays, lists, dictionaries, etc.)

PHP allows you to create an array simply by referencing the first item.

$myArray[0] = "Hello";
$myArray[1] = "World!";
echo $myArray[0].' '.$myArray[1];

And if you don’t want to have to keep a count and just keep appending on the end, you can do this:

$cities[] = 'Edinburgh';
$cities[] = 'Glasgow';
$cities[] = 'Aberdeen';
$cities[] = 'Dundee';
$cities[] = 'Inverness';
$cities[] = "Stirling";

Or, in an even more compact manner, like this:

$cities = array('Edinburgh', 'Glasgow', 'Aberdeen',
    'Dundee', 'Inverness', 'Stirling');

However, there is much more flexibility here. You can define the contents of a Dictionary like collection in the same way. Like this:

$capitals['Scotland'] = 'Edinburgh';
$capitals['England'] = 'London';
$capitals['Wales'] = 'Cardiff';
echo 'Scotland's capital is '.$capitals['Scotland'];

Like regular arrays, there is a compact way of expressing this too.

$capitals = array('Scotland' => 'Edinburgh',
    'England' => 'London', 'Wales' => 'Cardiff');

You can also use the formatting options that defining a string with double quotes permits in order to put the value of an array element into a string. Like this:

$capitals = array('Scotland' => 'Edinburgh',
    'England' => 'London', 'Wales' => 'Cardiff');
echo "The capital of Wales is {$capitals['Wales']}";

Finally, to remove an item from the array you can use the unset

unset($capitals['England']);

However, be aware that the indexes don’t move up if you remove an element, so for example, the following will fail:

$stuff = array('Zero','One', 'Two', 'Three', 'Four');
unset($stuff[1]);
echo 'Element 1 = '.$stuff[1];