debug-backtrace.xml

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<refentry xml:id="function.debug-backtrace" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>debug_backtrace</refname>
  <refpurpose>Generates a backtrace</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>array</type><methodname>debug_backtrace</methodname>
   <methodparam choice="opt"><type>int</type><parameter>options</parameter><initializer><constant>DEBUG_BACKTRACE_PROVIDE_OBJECT</constant></initializer></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>limit</parameter><initializer>0</initializer></methodparam>
  </methodsynopsis>
  <para>
   <function>debug_backtrace</function> generates a PHP backtrace.
  </para>
 </refsect1>
 
 <refsect1 role="parameters"><!-- {{{ -->
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>options</parameter></term>
     <listitem>
      <para>
       This parameter is a bitmask for the following options:
       <table>
        <title><function>debug_backtrace</function> options</title>
        <tgroup cols="2">
         <tbody>
          <row>
           <entry>DEBUG_BACKTRACE_PROVIDE_OBJECT</entry>
           <entry>
            Whether or not to populate the "object" index.
           </entry>
          </row>
          <row>
           <entry>DEBUG_BACKTRACE_IGNORE_ARGS</entry>
           <entry>
            Whether or not to omit the "args" index, and thus all the function/method arguments,
            to save memory.
           </entry>
          </row>
         </tbody>
        </tgroup>
       </table>
       <note>
        <para>
         There are four possible combinations:
         <table>
          <title><function>debug_backtrace</function> options</title>
          <tgroup cols="2">
           <tbody>
            <row>
             <entry><code>debug_backtrace()</code></entry>
             <entry morerows="2" valign="middle">
              Populates both indexes
             </entry>
            </row>
            <row>
             <entry><code>debug_backtrace(DEBUG_BACKTRACE_PROVIDE_OBJECT)</code></entry>
            </row>
            <row>
             <entry><code>debug_backtrace(1)</code></entry>
            </row>
            <row>
             <entry><code>debug_backtrace(0)</code></entry>
             <entry valign="middle">
              Omits index <literal>"object"</literal> and populates index <literal>"args"</literal>.
             </entry>
            </row>
            <row>
             <entry><code>debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS)</code></entry>
             <entry morerows="1" valign="middle">
              Omits index <literal>"object"</literal> <emphasis>and</emphasis> index <literal>"args"</literal>.
             </entry>
            </row>
            <row>
             <entry><code>debug_backtrace(2)</code></entry>
            </row>
            <row>
             <entry><code>debug_backtrace(DEBUG_BACKTRACE_PROVIDE_OBJECT|DEBUG_BACKTRACE_IGNORE_ARGS)</code></entry>
             <entry morerows="1" valign="middle">
              Populate index <literal>"object"</literal> <emphasis>and</emphasis> omit index <literal>"args"</literal>.
             </entry>
            </row>
            <row>
             <entry><code>debug_backtrace(3)</code></entry>
            </row>
           </tbody>
          </tgroup>
         </table>
        </para>
       </note>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>limit</parameter></term>
     <listitem>
      <para>
       This parameter can be used to limit the number of stack frames returned.
       By default (<parameter>limit</parameter>=<literal>0</literal>) it returns all stack frames.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1><!-- }}} -->
 
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns an array of associative <type>array</type>s. The possible returned elements
   are as follows:
  </para>
  <para>
   <table>
    <title>Possible returned elements from <function>debug_backtrace</function></title>
    <tgroup cols="3">
     <thead>
      <row>
       <entry>&Name;</entry>
       <entry>&Type;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>function</entry>
       <entry><type>string</type></entry>
       <entry>
        The current function name.  See also
        <link linkend="language.constants.predefined">__FUNCTION__</link>.
       </entry>
      </row>
      <row>
       <entry>line</entry>
       <entry><type>int</type></entry>
       <entry>
        The current line number.  See also
        <link linkend="language.constants.predefined">__LINE__</link>.
       </entry>
      </row>
      <row>
       <entry>file</entry>
       <entry><type>string</type></entry>
       <entry>
        The current file name.  See also
        <link linkend="language.constants.predefined">__FILE__</link>.
       </entry>
      </row>
      <row>
       <entry>class</entry>
       <entry><type>string</type></entry>
       <entry>
        The current <link linkend="language.oop5">class</link> name.  See also
        <link linkend="language.constants.predefined">__CLASS__</link>
       </entry>
      </row>
      <row>
       <entry>object</entry>
       <entry><type>object</type></entry>
       <entry>
        The current <link linkend="language.oop5">object</link>.
       </entry>
      </row>
      <row>
       <entry>type</entry>
       <entry><type>string</type></entry>
       <entry>
        The current call type. If a method call, "-&gt;" is returned. If a static
        method call, "::" is returned. If a function call, nothing is returned.
       </entry>
      </row>
      <row>
       <entry>args</entry>
       <entry><type>array</type></entry>
       <entry>
        If inside a function, this lists the functions arguments.  If
        inside an included file, this lists the included file name(s).
       </entry>
      </row>
     </tbody>
    </tgroup>
   </table>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>debug_backtrace</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
// filename: /tmp/a.php

function a_test($str)
{
    echo "\nHi: $str";
    var_dump(debug_backtrace());
}

a_test('friend');
?>

<?php
// filename: /tmp/b.php
include_once '/tmp/a.php';
?>
]]>
    </programlisting>
    <para>
     Results similar to the following when executing
     <filename>/tmp/b.php</filename>:
    </para>
    <screen>
<![CDATA[
Hi: friend
array(2) {
[0]=>
array(4) {
    ["file"] => string(10) "/tmp/a.php"
    ["line"] => int(10)
    ["function"] => string(6) "a_test"
    ["args"]=>
    array(1) {
      [0] => &string(6) "friend"
    }
}
[1]=>
array(4) {
    ["file"] => string(10) "/tmp/b.php"
    ["line"] => int(2)
    ["args"] =>
    array(1) {
      [0] => string(10) "/tmp/a.php"
    }
    ["function"] => string(12) "include_once"
  }
}
]]>
    </screen>
   </example>
  </para>
 </refsect1>
 
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>trigger_error</function></member>
    <member><function>debug_print_backtrace</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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