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   </p>
   <p class="simpara">
    This function is quite useless since every time it is called it
    sets <var class="varname">$a</var> to <i>0</i> and prints
    &quot;0&quot;.  The <var class="varname">$a</var>++ which increments the
    variable serves no purpose since as soon as the function exits the
    <var class="varname">$a</var> variable disappears.  To make a useful
    counting function which will not lose track of the current count,
    the <var class="varname">$a</var> variable is declared static:
   </p>
   <p class="para">
    <div class="example">
     <p><b>Example #5 Example use of static variables</b></p>
     <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">Test</span><span style="color: #007700">()<br />{<br />&nbsp;&nbsp;&nbsp;&nbsp;static&nbsp;</span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #0000BB">$a</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$a</span><span style="color: #007700">++;<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
     </div>

    </div>
   </p>
   <p class="simpara">
    Now, every time the Test() function is called it will print the
    value of <var class="varname">$a</var> and increment it.
   </p>

   <p class="simpara">
    Static variables also provide one way to deal with recursive
    functions. A recursive function is one which calls itself.  Care
    must be taken when writing a recursive function because it is
    possible to make it recurse indefinitely.  You must make sure you
    have an adequate way of terminating the recursion.  The following
    simple function recursively counts to 10, using the static
    variable <var class="varname">$count</var> to know when to stop:
   </p>
   <p class="para">
    <div class="example">
     <p><b>Example #6 Static variables with recursive functions</b></p>
     <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">Test</span><span style="color: #007700">()<br />{<br />&nbsp;&nbsp;&nbsp;&nbsp;static&nbsp;</span><span style="color: #0000BB">$count&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">;<br /><br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$count</span><span style="color: #007700">++;<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #0000BB">$count</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(</span><span style="color: #0000BB">$count&nbsp;</span><span style="color: #007700">&lt;&nbsp;</span><span style="color: #0000BB">10</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">Test</span><span style="color: #007700">();<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$count</span><span style="color: #007700">--;<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
     </div>

    </div>
   </p>

    <blockquote><p><b class="note">Note</b>:   
       
      Static variables may be declared as seen in the examples above. 
      Trying to assign values to these variables which are the 
      result of expressions will cause a parse error.
     <br /> 
       
      <div class="example">
       <p><b>Example #7 Declaring static variables</b></p>
       <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">foo</span><span style="color: #007700">(){<br />&nbsp;&nbsp;&nbsp;&nbsp;static&nbsp;</span><span style="color: #0000BB">$int&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">0</span><span style="color: #007700">;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;correct&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">static&nbsp;</span><span style="color: #0000BB">$int&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">+</span><span style="color: #0000BB">2</span><span style="color: #007700">;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;wrong&nbsp;&nbsp;(as&nbsp;it&nbsp;is&nbsp;an&nbsp;expression)<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">static&nbsp;</span><span style="color: #0000BB">$int&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">sqrt</span><span style="color: #007700">(</span><span style="color: #0000BB">121</span><span style="color: #007700">);&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;wrong&nbsp;&nbsp;(as&nbsp;it&nbsp;is&nbsp;an&nbsp;expression&nbsp;too)<br /><br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$int</span><span style="color: #007700">++;<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #0000BB">$int</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
      </div>

     </div>
    <br /> 
   </p></blockquote>
  </div>

  <div id="language.variables.scope.references" class="sect2">
   <h3 class="title">References with global and static variables</h3>
   <p class="simpara">
    The Zend Engine 1, driving PHP 4, implements the
    <a href="language.variables.scope.html#language.variables.scope.static" class="link">static</a> and 
    <a href="language.variables.scope.html#language.variables.scope.global" class="link">global</a> modifier 
    for variables in terms of <a href="language.references.html" class="link">
    references</a>. For example, a true global variable
    imported inside a function scope with the <i>global</i>
    statement actually creates a reference to the global variable. This can
    lead to unexpected behaviour which the following example addresses:
   </p>

   <div class="informalexample">
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">test_global_ref</span><span style="color: #007700">()&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;global&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$obj&nbsp;</span><span style="color: #007700">=&nbsp;&amp;new&nbsp;</span><span style="color: #0000BB">stdclass</span><span style="color: #007700">;<br />}<br /><br />function&nbsp;</span><span style="color: #0000BB">test_global_noref</span><span style="color: #007700">()&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;global&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$obj&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">stdclass</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">test_global_ref</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">test_global_noref</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div>

   <p class="simpara">
    Executing this example will result in the following output:
   </p>

   <div class="example-contents"><pre>
NULL
object(stdClass)(0) {
}
   </pre></div>

   <p class="simpara">
    A similar behaviour applies to the <i>static</i> statement.
    References are not stored statically:
   </p>
   
   <div class="informalexample">
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;&amp;</span><span style="color: #0000BB">get_instance_ref</span><span style="color: #007700">()&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;static&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">;<br /><br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'Static&nbsp;object:&nbsp;'</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(!isset(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;Assign&nbsp;a&nbsp;reference&nbsp;to&nbsp;the&nbsp;static&nbsp;variable<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$obj&nbsp;</span><span style="color: #007700">=&nbsp;&amp;new&nbsp;</span><span style="color: #0000BB">stdclass</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">property</span><span style="color: #007700">++;<br />&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">;<br />}<br /><br />function&nbsp;&amp;</span><span style="color: #0000BB">get_instance_noref</span><span style="color: #007700">()&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;static&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">;<br /><br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'Static&nbsp;object:&nbsp;'</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(!isset(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;Assign&nbsp;the&nbsp;object&nbsp;to&nbsp;the&nbsp;static&nbsp;variable<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$obj&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">stdclass</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">property</span><span style="color: #007700">++;<br />&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">$obj1&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">get_instance_ref</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">$still_obj1&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">get_instance_ref</span><span style="color: #007700">();<br />echo&nbsp;</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$obj2&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">get_instance_noref</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">$still_obj2&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">get_instance_noref</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div>

   <p class="simpara">
    Executing this example will result in the following output:
   </p>

   <div class="example-contents"><pre>
Static object: NULL
Static object: NULL

Static object: NULL
Static object: object(stdClass)(1) {
  [&quot;property&quot;]=&gt;
  int(1)
}
   </pre></div>

   <p class="simpara">
    This example demonstrates that when assigning a reference to a static
    variable, it&#039;s not <em class="emphasis">remembered</em> when you call the
    <i>&amp;get_instance_ref()</i> function a second time.
   </p>
   </div>
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