StringTemplate

StringTemplate is a very simple string template engine for php.

I've written it to have a thing like sprintf, but with named and nested substitutions.

For installing instructions, go to the end of this README.

Why

I have often struggled against sprintf's lack of a named placeholders feature, so I have decided to write once and for all a simple component that allows you to render a template string in which placeholders are named.

Furthermore, its placeholders can be nested as much as you want (multidimensional arrays allowed).

Usage

Simply create an instance of StringTemplate\Engine, and use its render method.

Placeholders are delimited by default by { and }, but you can specify others through the class constructor.

$engine = new StringTemplate\Engine;

//Scalar value: returns "This is my value: nic"
$engine->render("This is my value: {}", 'nic');

You can also provide an array value:

//Array value: returns "My name is Nicolò Martini"
$engine->render("My name is {name} {surname}", ['name' => 'Nicolò', 'surname' => 'Martini']);

Nested array values are allowed too! Example:

//Nested array value: returns "My name is Nicolò and her name is Gabriella"
$engine->render(
    "My name is {me.name} and her name is {her.name}",
    [
        'me' => ['name' => 'Nicolò'],
        'her' => ['name' => 'Gabriella']
    ]);

Object values will be converted to strings:

class Foo { function __toString() { return 'foo'; }

//Returns "foo: bar"
$engine->render(
    "{val}: bar",
    ['val' => new Foo]);

You can change the delimiters as you want:

$engine = new StringTemplate\Engine(':', '');

//Returns I am Nicolò Martini
$engine->render(
    "I am :name :surname",
    [
        'name' => 'Nicolò',
        'surname' => 'Martini'
    ]);

SprintfEngine

You can use a more powerful version of the engine if you want to specify convertion specifications for placeholders. The conversion syntax is identical to sprintf one, you need only to specify the optional parameter after the placeholder name.

Example:

$engine = new StringTemplate\SprintfEngine;

//Returns I have 1.2 (1.230000E+0) apples.
   $engine->render(
       "I have {num%.1f} ({num%.6E}) {fruit}.",
       [
           'num' => 1.23,
           'fruit' => 'apples'
       ]
   )

Keep in mind that power comes at a cost: SprintfEngine is 3 times slower than Engine (although if there are no '%' in the template string then performance is almost the same).

NestedKeyIterator and NestedKeyArray

Internally the engine iterates through the value array with the NestedKeyIterator. NestedKeyIterator iterates through multi-dimensional arrays giving as key the imploded keys stack.

It can be useful even if you don't need the Engine. Keep in mind that it is an RecursiveIteratorIterator, and so you have to pass a RecursiveIterator to its constructor (or, better, a StringTemplate\RecursiveArrayOnlyIterator if you do not want to iterate through objects).

Example:

use StringTemplate\NestedKeyIterator;
use StringTemplate\RecursiveArrayOnlyIterator;

$ary = [
    '1' => 'foo',
    '2' => [
        '1' => 'bar',
        '2' => ['1' => 'fog']
    ],
    '3' => [1, 2, 3]
];

$iterator = new NestedKeyIterator(new RecursiveArrayIterator($ary));

foreach ($iterator as $key => $value)
    echo "$key: $value\n";

// Prints
// 1: foo
// 2.1: bar
// 2.2.1: fog
// 3.0: 1
// 3.1: 2
// 3.2: 3

NestedKeyArray

In addition to iteration with nested keys, the library offers a class that allows you to access a multidimensional array with flatten nested keys as the ones seen above. It's called NestedKeyArray.

Example:

use StringTemplate\NestedKeyArray;

$ary = [
    '1' => 'foo',
    '2' => [
        '1' => 'bar',
        '2' => ['1' => 'fog']
    ],
    '3' => [1, 2, 3]
];

$nestedKeyArray = new NestedKeyArray($ary);

echo $nestedKeyArray['2.1']; //Prints 'bar'
$nestedKeyArray['2.1'] = 'new bar';
unset($nestedKeyArray['2.2']);
isset($nestedKeyArray['2.1']); //Returns true

foreach ($iterator as $key => $value)
    echo "$key: $value\n";

// Prints
// 1: foo
// 2.1: new bar
// 3.0: 1
// 3.1: 2
// 3.2: 3

Where is it used

I use StringTemplate in DomainSpecificQuery to implement the Lucene\TemplateExpression class.

Install

The best way to install StringTemplate is through composer.

Just create a composer.json file for your project:

{
    "require": {
        "nicmart/string-template": "~0.1"
    }
}

Then you can run these two commands to install it:

$ curl -s http://getcomposer.org/installer | php
$ php composer.phar install

or simply run composer install if you have have already installed the composer globally.

Then you can include the autoloader, and you will have access to the library classes:

<?php
require 'vendor/autoload.php';