# Zend_Uri

## Overview

`Zend_Uri` is a component that aids in manipulating and validating Uniform Resource Identifiers (URIs). `Zend_Uri` exists primarily to service other components such as `Zend_Http_Client` but is also useful as a standalone utility.

URIs always begin with a scheme, followed by a colon. The construction of the many different schemes varies significantly. The `Zend_Uri` class provides a factory that returns a subclass of itself which specializes in each scheme. The subclass will be named `Zend_Uri_<scheme>`, where `<scheme>` is the scheme lowercased with the first letter capitalized. An exception to this rule is HTTPS, which is also handled by `Zend_Uri_Http`.

## Creating a New URI

`Zend_Uri` will build a new URI from scratch if only a scheme is passed to `Zend_Uri::factory()`.

### Creating a New URI with Zend_Uri::factory()

    // To create a new URI from scratch, pass only the scheme.
    $uri = Zend_Uri::factory('http');

    // $uri instanceof Zend_Uri_Http

To create a new URI from scratch, pass only the scheme to `Zend_Uri::factory()` At the time of writing, `Zend_Uri` only supports the HTTP and HTTPS schemes. . If an unsupported scheme is passed, a `Zend_Uri_Exception` will be thrown.

If the scheme or URI passed is supported, `Zend_Uri::factory()` will return a subclass of itself that specializes in the scheme to be created.

## Manipulating an Existing URI

To manipulate an existing URI, pass the entire URI to `Zend_Uri::factory()`.

### Manipulating an Existing URI with Zend_Uri::factory()

    // To manipulate an existing URI, pass it in.
    $uri = Zend_Uri::factory('http://www.zend.com');

    // $uri instanceof Zend_Uri_Http

The URI will be parsed and validated. If it is found to be invalid, a `Zend_Uri_Exception` will be thrown immediately. Otherwise, `Zend_Uri::factory()` will return a subclass of itself that specializes in the scheme to be manipulated.

## URI Validation

The `Zend_Uri::check()` function can be used if only validation of an existing URI is needed.

### URI Validation with Zend_Uri::check()

    // Validate whether a given URI is well formed
    $valid = Zend_Uri::check('http://uri.in.question');

    // $valid is TRUE for a valid URI, or FALSE otherwise.

`Zend_Uri::check()` returns a boolean, which is more convenient than using `Zend_Uri::factory()` and catching the exception.

### Allowing "Unwise" characters in URIs

By default, `Zend_Uri` will not accept the following characters, defined by the RFC as "unwise" and invalid: `"{", "}", "|", "\", "^", "`"`. However, many implementations do accept these characters as valid.

`Zend_Uri` can be set to accept these "unwise" characters by setting the 'allow_unwise' option to boolean TRUE using the `Zend_Uri`::setConfig() method:

#### Allowing special characters in URIs

    // Contains '|' symbol
    // Normally, this would return false:
    $valid = Zend_Uri::check('http://example.com/?q=this|that');

    // However, you can allow "unwise" characters
    Zend_Uri::setConfig(array('allow_unwise' => true));
    // will return 'true'
    $valid = Zend_Uri::check('http://example.com/?q=this|that');

    // Reset the 'allow_unwise' value to the default FALSE
    Zend_Uri::setConfig(array('allow_unwise' => false));

`Zend_Uri::setConfig()` sets configuration options globally. It is recommended to reset the 'allow_unwise' option to 'false' like in the example above, unless you are certain you want to always allow unwise characters globally.

## Common Instance Methods

Every instance of a `Zend_Uri` subclass (e.g. `Zend_Uri_Http`) has several instance methods that are useful for working with any kind of URI.

### Getting the Scheme of the URI

The scheme of the URI is the part of the URI that precedes the colon. For example, the scheme of `http://www.zend.com` is `http`.

#### Getting the Scheme from a Zend_Uri_* Object

    $uri = Zend_Uri::factory('http://www.zend.com');

    $scheme = $uri->getScheme();  // "http"

The `getScheme()` instance method returns only the scheme part of the URI object.

### Getting the Entire URI

#### Getting the Entire URI from a Zend_Uri_* Object

    $uri = Zend_Uri::factory('http://www.zend.com');

    echo $uri->getUri();  // "http://www.zend.com"

The `getUri()` method returns the string representation of the entire URI.

### Validating the URI

`Zend_Uri::factory()` will always validate any URI passed to it and will not instantiate a new `Zend_Uri` subclass if the given URI is found to be invalid. However, after the `Zend_Uri` subclass is instantiated for a new URI or a valid existing one, it is possible that the URI can then later become invalid after it is manipulated.

#### Validating a Zend_Uri_* Object

    $uri = Zend_Uri::factory('http://www.zend.com');

    $isValid = $uri->valid();  // TRUE

The `valid()` instance method provides a means to check that the URI object is still valid.