Dana\Interpolator

Interpolator is a very simple string-interpolation library for PHP. It uses a syntax which combines features of Ruby, Jinja/Twig, and bash — including Jinja/Twig-style 'filters'.

Usage

$interpolator = new Interpolator();

// Basic usage: Both of these print 'Hello, dana!'
echo $interpolator->render('Hello, %{0}!', ['dana']), "\n";
echo $interpolator->render('Hello, %{name}!', ['name' => 'dana']), "\n";

// Filter usage: This prints 'Hello, DANA!' (u = upper-case)
echo $interpolator->render('Hello, %{0|u}!', ['dana']), "\n";

// Filter usage: This prints 'Hello, "DANA"!' (u = upper-case, j = JSON-encode)
echo $interpolator->render('Hello, %{0|uj}!', ['dana']), "\n";

// Filter usage: This prints 'Hello, 38095!' (c = CRC32, d = extract digits)
echo $interpolator->render('Hello, %{0|cd}!', ['dana']), "\n";

Interpolator's render() method is its most useful — it performs the actual interpolation and then returns the result. render() takes two arguments: the string to be interpolated, and an array of 'fixtures' (values which might be injected into the string). When a place-holder (%{foo}) is encountered, that place-holder name (foo) will be looked up in the keys of the fixtures array, and the associated value will be inserted into the string where the place-holder used to be.

Filters

Each place-holder may optionally be suffixed by a pipe (|) and one or more single-character filter specifiers. Most of the available filters are used for escaping and hashing — for example, the e filter specifier passes the fixture value through escapeshellarg() before rendering it, and the m specifier hashes the value with MD5. There are also filters for case conversion (l, u), white-space manipulation (t, w, W), &c. Filters may be chained together — for example, lhj will convert the value to lower-case, then pass it through htmlspecialchars(), then pass it through json_encode() (in that exact order).

This is a list of the default filter specifiers and their behaviours:

a  Extract letters [A-Za-z] from the string
b  Encode the string using base64
B  Encode the string using 'URL-safe' base64
c  Hash the string with CRC32
C  Hash the string with CRC32b
d  Extract digits [0–9] from the string
e  Escape the string for use as a shell argument (escapeshellarg())
f  Escape the string for use in a URL (rawurlencode()), but preserve slashes
h  Escape the string for use in HTML (htmlspecialchars())
H  Escape the string for use in HTML (htmlentities())
j  Escape the string for use in JSON (json_encode())
l  Convert the string to lower-case (mb_strtolower())
L  Convert the string to lower-case (strtolower())
m  Hash the string with MD5
p  Escape the string for use in a PCRE regular-expression pattern (preg_quote())
r  Escape the string for use in a URL (rawurlencode())
R  Escape the string for use in a URL (urlencode())
s  Hash the string with SHA1
S  Hash the string with SHA256
t  Trim the string of leading/trailing white space (trim())
u  Convert the string to upper-case (mb_strtoupper())
U  Convert the string to upper-case (strtoupper())
w  Collapse consecutive white space in the string into a single space
W  Remove all white space from the string

You don't have to use the defaults though — you can override some or all of them using the setFilter() and setFilters() methods:

$interpolator = new Interpolator();

// Replace all default filters by our own
$interpolator->setFilters(['a' => 'ucfirst']);

// This prints 'Foo'
echo $interpolator->render('%{0|a}', ['foo']), "\n";

Interpolator also supports auto filters — filters which are applied automatically after all other filter processing has completed. This is particularly useful for creating HTML templates, for example. Auto filters can be surpressed using the special - filter specifier.

$interpolator = new Interpolator();

// Apply htmlspecialchars() as an auto filter
$interpolator->setAutoFilters('h');

// This prints 'FOO&BAR'
echo $interpolator->render('%{0|u}', ['foo&bar']), "\n";

// This prints 'FOO&BAR' (auto filters suppressed)
echo $interpolator->render('%{0|u-}', ['foo&bar']), "\n";

Misc.

By default, when Interpolator encounters a missing fixture or a fixture that can't be converted to a string, it throws an exception. You can disable this 'strict' behaviour by passing an option to the constructor:

// Silently ignore missing/mistyped fixtures
$interpolator = new Interpolator(['strict' => false]);

Note that the presence of an illegal filter specifier will continue to raise an exception even when strict mode is disabled.

To do

• Better documentation
• More tests

Licence

MIT.