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<div class="section" id="helper-functions">
<h1>Helper Functions<a class="headerlink" href="#helper-functions" title="Permalink to this headline">¶</a></h1>
<p>Helpers, as the name suggests, help you with tasks. Each helper file is
simply a collection of functions in a particular category. There are <strong>URL
Helpers</strong>, that assist in creating links, there are Form Helpers that help
you create form elements, <strong>Text Helpers</strong> perform various text formatting
routines, <strong>Cookie Helpers</strong> set and read cookies, File Helpers help you
deal with files, etc.</p>
<p>Unlike most other systems in CodeIgniter, Helpers are not written in an
Object Oriented format. They are simple, procedural functions. Each
helper function performs one specific task, with no dependence on other
functions.</p>
<p>CodeIgniter does not load Helper Files by default, so the first step in
using a Helper is to load it. Once loaded, it becomes globally available
in your <a class="reference internal" href="controllers.html"><span class="doc">controller</span></a> and
<a class="reference internal" href="views.html"><span class="doc">views</span></a>.</p>
<p>Helpers are typically stored in your <strong>system/helpers</strong>, or
<strong>application/helpers directory</strong>. CodeIgniter will look first in your
<strong>application/helpers directory</strong>. If the directory does not exist or the
specified helper is not located there CI will instead look in your
global <em>system/helpers/</em> directory.</p>
<div class="section" id="loading-a-helper">
<h2>Loading a Helper<a class="headerlink" href="#loading-a-helper" title="Permalink to this headline">¶</a></h2>
<p>Loading a helper file is quite simple using the following method:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">helper</span><span class="p">(</span><span class="s1">'name'</span><span class="p">);</span>
</pre></div>
</div>
<p>Where <strong>name</strong> is the file name of the helper, without the .php file
extension or the “helper” part.</p>
<p>For example, to load the <strong>URL Helper</strong> file, which is named
<strong>url_helper.php</strong>, you would do this:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">helper</span><span class="p">(</span><span class="s1">'url'</span><span class="p">);</span>
</pre></div>
</div>
<p>A helper can be loaded anywhere within your controller methods (or
even within your View files, although that’s not a good practice), as
long as you load it before you use it. You can load your helpers in your
controller constructor so that they become available automatically in
any function, or you can load a helper in a specific function that needs
it.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The Helper loading method above does not return a value, so
don’t try to assign it to a variable. Just use it as shown.</p>
</div>
</div>
<div class="section" id="loading-multiple-helpers">
<h2>Loading Multiple Helpers<a class="headerlink" href="#loading-multiple-helpers" title="Permalink to this headline">¶</a></h2>
<p>If you need to load more than one helper you can specify them in an
array, like this:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-></span><span class="na">load</span><span class="o">-></span><span class="na">helper</span><span class="p">(</span>
<span class="k">array</span><span class="p">(</span><span class="s1">'helper1'</span><span class="p">,</span> <span class="s1">'helper2'</span><span class="p">,</span> <span class="s1">'helper3'</span><span class="p">)</span>
<span class="p">);</span>
</pre></div>
</div>
</div>
<div class="section" id="auto-loading-helpers">
<h2>Auto-loading Helpers<a class="headerlink" href="#auto-loading-helpers" title="Permalink to this headline">¶</a></h2>
<p>If you find that you need a particular helper globally throughout your
application, you can tell CodeIgniter to auto-load it during system
initialization. This is done by opening the <strong>application/config/autoload.php</strong>
file and adding the helper to the autoload array.</p>
</div>
<div class="section" id="using-a-helper">
<h2>Using a Helper<a class="headerlink" href="#using-a-helper" title="Permalink to this headline">¶</a></h2>
<p>Once you’ve loaded the Helper File containing the function you intend to
use, you’ll call it the way you would a standard PHP function.</p>
<p>For example, to create a link using the <code class="docutils literal"><span class="pre">anchor()</span></code> function in one of
your view files you would do this:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="o"><?</span><span class="nx">php</span> <span class="k">echo</span> <span class="nx">anchor</span><span class="p">(</span><span class="s1">'blog/comments'</span><span class="p">,</span> <span class="s1">'Click Here'</span><span class="p">);</span><span class="cp">?></span>
</pre></div>
</div>
<p>Where “Click Here” is the name of the link, and “blog/comments” is the
URI to the controller/method you wish to link to.</p>
</div>
<div class="section" id="extending-helpers">
<h2>“Extending” Helpers<a class="headerlink" href="#extending-helpers" title="Permalink to this headline">¶</a></h2>
<p>To “extend” Helpers, create a file in your <strong>application/helpers/</strong> folder
with an identical name to the existing Helper, but prefixed with <strong>MY_</strong>
(this item is configurable. See below.).</p>
<p>If all you need to do is add some functionality to an existing helper -
perhaps add a function or two, or change how a particular helper
function operates - then it’s overkill to replace the entire helper with
your version. In this case it’s better to simply “extend” the Helper.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The term “extend” is used loosely since Helper functions are
procedural and discrete and cannot be extended in the traditional
programmatic sense. Under the hood, this gives you the ability to
add to or or to replace the functions a Helper provides.</p>
</div>
<p>For example, to extend the native <strong>Array Helper</strong> you’ll create a file
named <strong>application/helpers/MY_array_helper.php</strong>, and add or override
functions:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// any_in_array() is not in the Array Helper, so it defines a new function</span>
<span class="k">function</span> <span class="nf">any_in_array</span><span class="p">(</span><span class="nv">$needle</span><span class="p">,</span> <span class="nv">$haystack</span><span class="p">)</span>
<span class="p">{</span>
<span class="nv">$needle</span> <span class="o">=</span> <span class="nb">is_array</span><span class="p">(</span><span class="nv">$needle</span><span class="p">)</span> <span class="o">?</span> <span class="nv">$needle</span> <span class="o">:</span> <span class="k">array</span><span class="p">(</span><span class="nv">$needle</span><span class="p">);</span>
<span class="k">foreach</span> <span class="p">(</span><span class="nv">$needle</span> <span class="k">as</span> <span class="nv">$item</span><span class="p">)</span>
<span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="nb">in_array</span><span class="p">(</span><span class="nv">$item</span><span class="p">,</span> <span class="nv">$haystack</span><span class="p">))</span>
<span class="p">{</span>
<span class="k">return</span> <span class="k">TRUE</span><span class="p">;</span>
<span class="p">}</span>
<span class="p">}</span>
<span class="k">return</span> <span class="k">FALSE</span><span class="p">;</span>
<span class="p">}</span>
<span class="c1">// random_element() is included in Array Helper, so it overrides the native function</span>
<span class="k">function</span> <span class="nf">random_element</span><span class="p">(</span><span class="nv">$array</span><span class="p">)</span>
<span class="p">{</span>
<span class="nb">shuffle</span><span class="p">(</span><span class="nv">$array</span><span class="p">);</span>
<span class="k">return</span> <span class="nb">array_pop</span><span class="p">(</span><span class="nv">$array</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
</div>
<div class="section" id="setting-your-own-prefix">
<h3>Setting Your Own Prefix<a class="headerlink" href="#setting-your-own-prefix" title="Permalink to this headline">¶</a></h3>
<p>The filename prefix for “extending” Helpers is the same used to extend
libraries and core classes. To set your own prefix, open your
<strong>application/config/config.php</strong> file and look for this item:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$config</span><span class="p">[</span><span class="s1">'subclass_prefix'</span><span class="p">]</span> <span class="o">=</span> <span class="s1">'MY_'</span><span class="p">;</span>
</pre></div>
</div>
<p>Please note that all native CodeIgniter libraries are prefixed with <strong>CI_</strong>
so DO NOT use that as your prefix.</p>
</div>
</div>
<div class="section" id="now-what">
<h2>Now What?<a class="headerlink" href="#now-what" title="Permalink to this headline">¶</a></h2>
<p>In the Table of Contents you’ll find a list of all the available Helper
Files. Browse each one to see what they do.</p>
</div>
</div>
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