On 20/03/2008, Robin Vickery <robinv@xxxxxxxxx> wrote:
> Hiyah,
>
> Here's a trick you can use to evaluate expressions within strings. It
> may not be particularly useful, but I thought it was interesting.
>
> It exploits two things:
>
> 1. If you interpolate an array element within a string, the index of
> the element is evaluated as a php expression.
>
> 2. You can can make your own magic arrays by extending arrayObject.
>
>
> <?php
> class identityArrayObject extends arrayObject
> {
> public function offsetGet($index)
> {
> return $index;
> }
> }
>
> $eval = new identityArrayObject;
>
> print "The square root of {$eval[pow(2,2)]} is {$eval[sqrt(4)]} \n";
>
> print "Price: $price GBP ({$eval[$price * 1.175]} GBP including tax) \n";
>
> ?>
>
> You can extend it to add your own formatting elements:
>
> <?php
> class uppercaseArrayObject extends arrayObject
> {
> public function offsetGet($index)
> {
> return strtoupper($index);
> }
> }
>
> $U = new uppercaseArrayObject;
> $city = 'edinburgh';
>
> print "The capital of Scotland is $U[$city] \n";
> ?>
>
More generic:
<?php
class transformArrayObject extends arrayObject
{
protected $transform;
public function __construct($transform = null)
{
$this->transform = is_null($transform) ? array($this, 'identity')
: $transform;
}
public function offsetGet($index)
{
return call_user_func($this->transform, $index);
}
public function identity($index)
{
return $index;
}
}
$eval = new transformArrayObject;
$U = new transformArrayObject('strtoupper');
$u = new transformArrayObject('ucfirst');
$L = new transformArrayObject('strtolower');
$GBP = new transformArrayObject(create_function('$index', 'return
money_format("%n", $index);'));
$price = 50;
$tax = 1.175;
$city = 'EdInBurGH';
print "A ticket to $U[$city] is: $GBP[$price] ({$GBP[$price * $tax]}
including VAT)\n";
// A ticket to EDINBURGH is: £50.00 (£58.75 including VAT)
?>
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