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This is Pico's official HTTP parameters plugin to access GET and POST parameters in Twig templates.
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README.md

Pico HTTP Parameters

This is the repository of Pico's official HTTP parameters plugin.

Pico is a stupidly simple, blazing fast, flat file CMS. See http://picocms.org/ for more info.

PicoHttpParams allows theme developers to access HTTP GET and HTTP POST parameters in Twig templates using the url_param resp. form_param functions. This makes developing awesome themes for your Pico website easier than ever before.

This plugin basically wraps around PHP's filter_var() function. Here's a excerpt from PHP's documentation about the filter extension:

This extension filters data by either validating or sanitizing it. This is especially useful when the data source contains unknown (or foreign) data, like user supplied input. For example, this data may come from an HTML form.

There are two main types of filtering: validation and sanitization.

Validation is used to validate or check if the data meets certain qualifications. For example, passing in FILTER_VALIDATE_EMAIL will determine if the data is a valid email address, but will not change the data itself.

Sanitization will sanitize the data, so it may alter it by removing undesired characters. For example, passing in FILTER_SANITIZE_EMAIL will remove characters that are inappropriate for an email address to contain. That said, it does not validate the data.

Flags are optionally used with both validation and sanitization to tweak behaviour according to need. For example, passing in FILTER_FLAG_PATH_REQUIRED while filtering an URL will require a path (like /foo in http://example.org/foo) to be present.

Copyright © 1997-2016 The PHP Documentation Group, released under the Creative Commons Attribution 3.0 license

Install

Just download the latest release and upload the PicoHttpParams.php file to the plugins directory of your Pico installation (e.g. /var/www/html/pico/plugins/). The plugin is also available on Packagist.org and may be included in other projects via composer require phrozenbyte/pico-http-params. The plugin requires Pico 1.0+

This plugin is a backport of an feature that will be included in Pico's core starting with Pico 1.1. Even though this plugin is compatible with Pico 1.1 (and later), it doesn't provide any functionality when used together with Pico 1.1 (and later). Therefore you can safely remove this plugin on Pico 1.1 installations if no other installed plugin depends on it. However, you are not required to. Put briefly, manually installing this plugin makes sense with Pico 1.0 only.

Config

You can't configure this plugin, it's a utility plugin for theme developers.

Usage

Heads up! Input validation is hard! Always validate your input data the most paranoid way you can imagine. Always prefer validation filters over sanitization filters; be very careful with sanitization filters, you might create cross-site scripting vulnerabilities!

The PicoHttpParams::getUrlParameter() function resp. the url_param Twig function and the PicoHttpParams::getFormParameter() function resp. the form_param Twig function all accept the following parameters:

Variable Type Parameter Name Description
mixed $name name of the HTTP GET or HTTP POST variable
int | string $filter = '' ID (int) or name (string) of the filter to apply; if omitted, all functions will return false
mixed | array $options = null either a associative array of options to be used by the filter (e.g. [ 'default': 42 ]), or a scalar default value that will be returned when the HTTP GET or HTTP POST variable doesn't exist (optional)
int | string | int[] | string[] $flags = null either a bitwise disjunction of flags or a string with the significant part of a flag constant (the constant name is the result of FILTER_FLAG_ and the given string in ASCII-only uppercase); you may also pass an array of flags and flag strings (optional)

With a validation filter passed in, all functions return the validated value of the HTTP GET or HTTP POST parameter, or, provided that the value wasn't valid, either the given default value or false. With a sanitization filter passed in, all functions return the sanitized value of the HTTP GET or HTTP POST parameter. If the HTTP GET or HTTP POST variable doesn't exist, all functions will always return either the provided default value or null.

Examples

Pass the boolean HTTP GET parameter expand to expand a details section in your template:

<a href="{{ current_page.id|link('expand=yes') }}">Learn more...</a>

{% if url_param('expand', 'boolean') %}
    You're learning more right now! Isn't that great!?
{% endif %}

Ask a user about "the answer" using a HTML form and store his decision in the Twig variable the_answer. Use a regular expression to allow just values that are actually present in the HTML form.

<form action="" method="POST">
    <label for="the_answer">What is the answer?</label>
    <select id="the_answer" name="the_answer">
        <option></option>
        <option value="band">a Northern Irish hard rock and blues-rock band</option>
        <option value="42">42</option>
        <option value="what">What the hell are you talking about?</option>
    </select>
    <input type="submit" />
</form>

{% set the_answer = form_param('the_answer', 'validate_regexp', { 'regexp': '/^(band|42|what)$/' }) %}

Ask a user how much he makes a year and claim that his amount is either sad or ridicilous because you make twice as much a year. Use the Twig variable amount and let the parameter default to 0. Use the FILTER_VALIDATE_FLOAT (float) filter, but tweak its behaviour by passing the FILTER_FLAG_ALLOW_THOUSAND flag - this allows the user to enter their amount with a thousand separator (e.g. 12,345.00).

<form action="" method="GET">
    <label for="amount">How much do you make a year?</label>
    <input id="amount" name="amount" type="text" />
    <input type="submit" />
</form>

{% set amount = url_param('amount', 'float', 0, 'allow_thousand') %}
{% if amount > 0 %}
    {% if amount < 10 %}
        You make just {{ amount }} cat pictures a year? Oh, that's sad... :-(
    {% else %}
        Impressive... Not! This is ridiculous! I make {{ amount * 2 }} cat pictures a year!
    {% endif %}
{% endif %}
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