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425 <div class="section" id="hooks-extending-the-framework-core">
426<h1>Hooks - Extending the Framework Core<a class="headerlink" href="#hooks-extending-the-framework-core" title="Permalink to this headline"></a></h1>
427<p>CodeIgniter’s Hooks feature provides a means to tap into and modify the
428inner workings of the framework without hacking the core files. When
429CodeIgniter runs it follows a specific execution process, diagramed in
430the <a class="reference internal" href="../overview/appflow.html"><span class="doc">Application Flow</span></a> page. There may be
431instances, however, where you’d like to cause some action to take place
432at a particular stage in the execution process. For example, you might
433want to run a script right before your controllers get loaded, or right
434after, or you might want to trigger one of your own scripts in some
435other location.</p>
436<div class="section" id="enabling-hooks">
437<h2>Enabling Hooks<a class="headerlink" href="#enabling-hooks" title="Permalink to this headline"></a></h2>
438<p>The hooks feature can be globally enabled/disabled by setting the
439following item in the <strong>application/config/config.php</strong> file:</p>
440<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$config</span><span class="p">[</span><span class="s1">&#39;enable_hooks&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="k">TRUE</span><span class="p">;</span>
441</pre></div>
442</div>
443</div>
444<div class="section" id="defining-a-hook">
445<h2>Defining a Hook<a class="headerlink" href="#defining-a-hook" title="Permalink to this headline"></a></h2>
446<p>Hooks are defined in the <strong>application/config/hooks.php</strong> file.
447Each hook is specified as an array with this prototype:</p>
448<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$hook</span><span class="p">[</span><span class="s1">&#39;pre_controller&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="k">array</span><span class="p">(</span>
449 <span class="s1">&#39;class&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;MyClass&#39;</span><span class="p">,</span>
450 <span class="s1">&#39;function&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;Myfunction&#39;</span><span class="p">,</span>
451 <span class="s1">&#39;filename&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;Myclass.php&#39;</span><span class="p">,</span>
452 <span class="s1">&#39;filepath&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;hooks&#39;</span><span class="p">,</span>
453 <span class="s1">&#39;params&#39;</span> <span class="o">=&gt;</span> <span class="k">array</span><span class="p">(</span><span class="s1">&#39;beer&#39;</span><span class="p">,</span> <span class="s1">&#39;wine&#39;</span><span class="p">,</span> <span class="s1">&#39;snacks&#39;</span><span class="p">)</span>
454<span class="p">);</span>
455</pre></div>
456</div>
457<p><strong>Notes:</strong></p>
458<p>The array index correlates to the name of the particular hook point you
459want to use. In the above example the hook point is pre_controller. A
460list of hook points is found below. The following items should be
461defined in your associative hook array:</p>
462<ul class="simple">
463<li><strong>class</strong> The name of the class you wish to invoke. If you prefer to
464use a procedural function instead of a class, leave this item blank.</li>
465<li><strong>function</strong> The function (or method) name you wish to call.</li>
466<li><strong>filename</strong> The file name containing your class/function.</li>
467<li><strong>filepath</strong> The name of the directory containing your script.
468Note:
469Your script must be located in a directory INSIDE your <em>application/</em>
470directory, so the file path is relative to that directory. For example,
471if your script is located in <em>application/hooks/</em>, you will simply use
472‘hooks’ as your filepath. If your script is located in
473<em>application/hooks/utilities/</em> you will use ‘hooks/utilities’ as your
474filepath. No trailing slash.</li>
475<li><strong>params</strong> Any parameters you wish to pass to your script. This item
476is optional.</li>
477</ul>
478<p>You can also use lambda/anoymous functions (or closures) as hooks, with
479a simpler syntax:</p>
480<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$hook</span><span class="p">[</span><span class="s1">&#39;post_controller&#39;</span><span class="p">]</span> <span class="o">=</span> <span class="k">function</span><span class="p">()</span>
481<span class="p">{</span>
482 <span class="cm">/* do something here */</span>
483<span class="p">};</span>
484</pre></div>
485</div>
486</div>
487<div class="section" id="multiple-calls-to-the-same-hook">
488<h2>Multiple Calls to the Same Hook<a class="headerlink" href="#multiple-calls-to-the-same-hook" title="Permalink to this headline"></a></h2>
489<p>If want to use the same hook point with more than one script, simply
490make your array declaration multi-dimensional, like this:</p>
491<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$hook</span><span class="p">[</span><span class="s1">&#39;pre_controller&#39;</span><span class="p">][]</span> <span class="o">=</span> <span class="k">array</span><span class="p">(</span>
492 <span class="s1">&#39;class&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;MyClass&#39;</span><span class="p">,</span>
493 <span class="s1">&#39;function&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;MyMethod&#39;</span><span class="p">,</span>
494 <span class="s1">&#39;filename&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;Myclass.php&#39;</span><span class="p">,</span>
495 <span class="s1">&#39;filepath&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;hooks&#39;</span><span class="p">,</span>
496 <span class="s1">&#39;params&#39;</span> <span class="o">=&gt;</span> <span class="k">array</span><span class="p">(</span><span class="s1">&#39;beer&#39;</span><span class="p">,</span> <span class="s1">&#39;wine&#39;</span><span class="p">,</span> <span class="s1">&#39;snacks&#39;</span><span class="p">)</span>
497<span class="p">);</span>
498
499<span class="nv">$hook</span><span class="p">[</span><span class="s1">&#39;pre_controller&#39;</span><span class="p">][]</span> <span class="o">=</span> <span class="k">array</span><span class="p">(</span>
500 <span class="s1">&#39;class&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;MyOtherClass&#39;</span><span class="p">,</span>
501 <span class="s1">&#39;function&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;MyOtherMethod&#39;</span><span class="p">,</span>
502 <span class="s1">&#39;filename&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;Myotherclass.php&#39;</span><span class="p">,</span>
503 <span class="s1">&#39;filepath&#39;</span> <span class="o">=&gt;</span> <span class="s1">&#39;hooks&#39;</span><span class="p">,</span>
504 <span class="s1">&#39;params&#39;</span> <span class="o">=&gt;</span> <span class="k">array</span><span class="p">(</span><span class="s1">&#39;red&#39;</span><span class="p">,</span> <span class="s1">&#39;yellow&#39;</span><span class="p">,</span> <span class="s1">&#39;blue&#39;</span><span class="p">)</span>
505<span class="p">);</span>
506</pre></div>
507</div>
508<p>Notice the brackets after each array index:</p>
509<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$hook</span><span class="p">[</span><span class="s1">&#39;pre_controller&#39;</span><span class="p">][]</span>
510</pre></div>
511</div>
512<p>This permits you to have the same hook point with multiple scripts. The
513order you define your array will be the execution order.</p>
514</div>
515<div class="section" id="hook-points">
516<h2>Hook Points<a class="headerlink" href="#hook-points" title="Permalink to this headline"></a></h2>
517<p>The following is a list of available hook points.</p>
518<ul class="simple">
519<li><strong>pre_system</strong>
520Called very early during system execution. Only the benchmark and
521hooks class have been loaded at this point. No routing or other
522processes have happened.</li>
523<li><strong>pre_controller</strong>
524Called immediately prior to any of your controllers being called.
525All base classes, routing, and security checks have been done.</li>
526<li><strong>post_controller_constructor</strong>
527Called immediately after your controller is instantiated, but prior
528to any method calls happening.</li>
529<li><strong>post_controller</strong>
530Called immediately after your controller is fully executed.</li>
531<li><strong>display_override</strong>
532Overrides the <code class="docutils literal"><span class="pre">_display()</span></code> method, used to send the finalized page
533to the web browser at the end of system execution. This permits you
534to use your own display methodology. Note that you will need to
535reference the CI superobject with <code class="docutils literal"><span class="pre">$this-&gt;CI</span> <span class="pre">=&amp;</span> <span class="pre">get_instance()</span></code> and
536then the finalized data will be available by calling
537<code class="docutils literal"><span class="pre">$this-&gt;CI-&gt;output-&gt;get_output()</span></code>.</li>
538<li><strong>cache_override</strong>
539Enables you to call your own method instead of the <code class="docutils literal"><span class="pre">_display_cache()</span></code>
540method in the <a class="reference internal" href="../libraries/output.html"><span class="doc">Output Library</span></a>. This permits
541you to use your own cache display mechanism.</li>
542<li><strong>post_system</strong>
543Called after the final rendered page is sent to the browser, at the
544end of system execution after the finalized data is sent to the
545browser.</li>
546</ul>
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