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PHP, Web Forms and the Ternary Operator

Published on: October 1, 2009 @ 12:48:46 · 0 comments

If the great comedian Rodney Dangerfield were reincarnated as a programming contruct, he would undoubtedly return as the ternary operator. This is because the ternary operator, a powerful programming construct supported by most if not all of today's mainstream languages, just gets no respect, particularly from beginning programmers who sneer at its admittedly odd syntax. Yet to those programmers who look past its appearance, the ternary operator can be the life of the party time-and-again.

For those who aren't yet familiar with this syntactical gem, the ternary operator is an operator that accepts three operators. Written in pseudocode, its syntax looks like this:

$variable = condition ? if true : if false

Pretty strange, right? Let's look at a ternary operator as it would appear in actual PHP code:

$available = ($inventory > 0) ? "yes" : "no";

In this example, the variable $available will be assigned the string yes if $inventory is assigned a value greater than 0. Otherwise, $available will be assigned the string no. Of course, the same outcome could be had using an if-statement:

if ($inventory > 0) {
    $available = "yes";
} else {
    $available = "no";
}

As you can see, the ternary operator-based variation is far more succinct. This condensed form can be quite useful when HTML output is dependent upon some sort of dynamically changing situation, such as is the case when retrieving data from a database. For instance, I regularly use the ternary operator within the <select> tag when I need to pre-select a particular value in the list box. Here's an example:

01 <p>
02 Product:<br />
03 <select name="product-id">
04   <?php foreach($this->products AS $product) { ?>
05  <option value="<?= $product->id ?>" 
06  <?= $this->discount->product_id == $product->id ? "selected" : ""; ?>>
07  <?= $product->title; ?>
08  </option>
09   <?php } ?>
10 </select>
11 </p>

In this example, the ternary operator comes into play on line 06, where we're comparing the $this->discount object's product_id attribute value with that found in the $product object's id attribute. If equal, selected will be output, causing that particular option to be preset.

Given such capabilities, the next time you come across the ternary operator, raise a glass and give it some respect!

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