php-doc-en/faq/html.xml

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 <chapter id="faq.html">
  <title>PHP and HTML</title>
  <titleabbrev>PHP and HTML</titleabbrev>

  <para>
   PHP and HTML interact a lot : PHP generate HTML, and HTML
   has informations that will be sent to PHP.
  </para>

  <qandaset>
   <qandaentry id="faq.html.form-image">
    <question>
     <para>
      I'm trying to use an &lt;input type="image"&gt; tag, but 
      the $foo.x and $foo.y variables aren't available. 
      Where are they?
     </para>
    </question>
    <answer>
     <para>
      When submitting a form, it is possible to use an image instead of
      the standard submit button with a tag like:
      <programlisting>
<![CDATA[
<input type="image" src="image.gif" name="foo">
]]>
      </programlisting>
      When the user clicks somewhere on the image, the accompanying form
      will be transmitted to the server with two additional variables:
      foo.x and foo.y.
     </para>
     <para>
      Because $foo.x and $foo.y are invalid variable names in PHP, they are
      automagically converted to $foo_x and $foo_y.  That is, the periods
      are replaced with underscores.
     </para>
    </answer>
   </qandaentry>

   <qandaentry id="faq.html.arrays">
    <question>
     <para>How do I create arrays in a HTML &lt;form&gt;?</para>
    </question>
    <answer>
     <para>
      To get your &lt;form&gt; result sent as an array to your PHP script
      you name the &lt;input&gt;, &lt;select&gt; or &lt;textarea&gt;
      elements like this:
      <programlisting>
<![CDATA[
<input name="MyArray[]">
<input name="MyArray[]">
<input name="MyArray[]">
<input name="MyArray[]">
]]>
      </programlisting>
      Notice the square brackets after the variable name, that's what
      makes it an array. You can group the elements into different arrays
      by assigning the same name to different elements:
      <programlisting>
<![CDATA[
<input name="MyArray[]">
<input name="MyArray[]">
<input name="MyOtherArray[]">
<input name="MyOtherArray[]">
]]>
      </programlisting>
      This produces two arrays, MyArray and MyOtherArray, that gets sent
      to the PHP script.
      </para>
      <para>
       <note>
        <para>
         You need not use indices with arrays in HTML, although you can
         specify number or associative indices, so you can exactly specify
         what indices will contain the information provided by that
         input element. If you do not specify indices, the array gets
         filled in the order the elements appear in the form.
        </para>
       </note>
      </para>
      <para>
      For functions you can use to process these arrays once you get
      them into your scripts, please see the
      <link linkend="ref.array">Arrays section</link>.
     </para>
    </answer>
   </qandaentry>

   <qandaentry id="faq.html.select-multiple">
    <question>
     <para>
      How do I get all the results from a select multiple HTML tag? 
     </para>
    </question>
    <answer>
     <para>
      The select multiple tag in an HTML construct allows users to
      select multiple items from a list. These items are then passed
      to the action handler for the form. The problem is that they
      are all passed with the same widget name. ie.
      <programlisting>
<![CDATA[
<select name="var" multiple>
]]>
      </programlisting>
      Each selected option will arrive at the action handler as:
      <programlisting>
var=option1
var=option2
var=option3
      </programlisting>
      Each option will overwrite the contents of the previous
      <varname>$var</varname> variable. The solution is to use
      PHP's "array from form element" feature. The following
      should be used:
      <programlisting>
<![CDATA[
<select name="var[]" multiple>
]]>
      </programlisting>
      This tells PHP to treat <varname>$var</varname> as an array and
      each assignment of a value to var[] adds an item to the array.
      The first item becomes <varname>$var[0]</varname>, the next
      <varname>$var[1]</varname>, etc. The <function>count</function>
      function can be used to determine how many options were selected,
      and the <function>sort</function> function can be used to sort
      the option array if necessary.
     </para>
     <para>
      Note that if you are using JavaScript the <literal>[]</literal>
      on the element name might cause you problems when you try to
      refer to the element by name. Use it's numerical form element
      id instead, or enclose the variable name in single quotes and
      use that as the index to the elements array, for example:
      <programlisting>
variable = documents.forms[0].elements['var[]'];
      </programlisting>
     </para>
    </answer>
   </qandaentry>
  </qandaset>
 </chapter>

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