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      Custom Error Message Generation
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          <h1>
            HTML_Progress2 : The Definitive Guide
          </h1>
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                <th colspan="3" align="center">
                  Custom Error Message Generation
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                  <a accesskey="p" href="ch16s04.html">Prev</a>&nbsp;
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                  Chapter&nbsp;16.&nbsp;Error Handler
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                  &nbsp;<a accesskey="n" href="ch17.html">Next</a>
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    <div class="sect1" lang="en" xml:lang="en">
      <div class="titlepage">
        <h2 class="title c1">
          <a name="id4804070" id="id4804070"></a>Custom Error Message
          Generation
        </h2>
      </div>
      <div class="toc">
        <dl>
          <dt>
            <span class="sect2"><a href="ch16s05.html#id4804100">Option:
            message_callback</a></span>
          </dt>
          <dt>
            <span class="sect2"><a href="ch16s05.html#id4804127">Option:
            context_callback</a></span>
          </dt>
        </dl>
      </div>
      <p>
        In the default error class <code class=
        "classname">HTML_Progress2_Error</code> there are two methods designed
        for use with generating error messages efficiently. To use them, you
        must set the options <code class="literal">message_callback</code>, and
        <code class="literal">context_callback</code>.
      </p>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <h3 class="title">
            <a name="id4804100" id="id4804100"></a>Option: message_callback
          </h3>
        </div>
        <p>
          The default message handling callback (<code class=
          "methodname">HTML_Progress2_Error::_getErrorMessage</code>) get an
          array mapping error codes to error message templates, like so:
        </p>
        <div class="php c2">
          <ol>
            <li class="li1">
              <div class="de1">
                <span class="kw2">&lt;?php</span>
              </div>
            </li>
            <li class="li1">
              <div class="de1">
                <span class="re1">$messages</span> <span class="sy0">=</span>
                <span class="kw3">array</span><span class="br0">(</span>
              </div>
            </li>
            <li class="li1">
              <div class="de1">
                &nbsp; &nbsp; HTML_PROGRESS2_ERROR_UNKNOWN <span class=
                "sy0">=&gt;</span>
              </div>
            </li>
            <li class="li1">
              <div class="de1">
                &nbsp; &nbsp; &nbsp; &nbsp; <span class="st0">'unknown
                error'</span><span class="sy0">,</span>
              </div>
            </li>
            <li class="li1">
              <div class="de1">
                &nbsp; &nbsp; HTML_PROGRESS2_ERROR_INVALID_INPUT <span class=
                "sy0">=&gt;</span>
              </div>
            </li>
            <li class="li1">
              <div class="de1">
                &nbsp; &nbsp; &nbsp; &nbsp; <span class="st0">'invalid input,
                parameter #%paramnum% '</span>
              </div>
            </li>
            <li class="li1">
              <div class="de1">
                &nbsp; &nbsp; &nbsp; <span class="sy0">.</span> <span class=
                "st0">'"%var%" was expecting '</span>
              </div>
            </li>
            <li class="li1">
              <div class="de1">
                &nbsp; &nbsp; &nbsp; <span class="sy0">.</span> <span class=
                "st0">'"%expected%", instead got "%was%"'</span>
              </div>
            </li>
            <li class="li1">
              <div class="de1">
                <span class="br0">)</span><span class="sy0">;</span>
              </div>
            </li>
            <li class="li1">
              <div class="de1">
                <span class="kw2">?&gt;</span>
              </div>
            </li>
          </ol>
        </div>
        <p>
          Basically, if a variable name is enclosed in percent signs (%), it
          will be replaced with the value passed in the associative array.
        </p>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <h3 class="title">
            <a name="id4804127" id="id4804127"></a>Option: context_callback
          </h3>
        </div>
        <p>
          The default context handling callback (<code class=
          "methodname">HTML_Progress2_Error::getBackTrace</code>) gets an array
          of execution functions and discovers where the error was generated.
        </p>
      </div>
    </div>
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          HTML_Progress2 : The Definitive Guide
        </td>
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          v 2.4.0 : April 20, 2007
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            Error Context Display &nbsp;
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            &nbsp;Chapter&nbsp;17.&nbsp;Events to observe
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