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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 297078 $ -->
<sect2 xml:id="internals2.ze1.zendapi.printing" xmlns="http://docbook.org/ns/docbook">
<title>Printing Information</title>
<para>
Often it's necessary to print messages to the output stream from
your module, just as <function>print</function> would be used
within a script. PHP offers functions for most generic tasks, such
as printing warning messages, generating output for
<function>phpinfo</function>, and so on. The following sections
provide more details. Examples of these functions can be found on
the CD-ROM.
</para>
<sect3 xml:id="internals2.ze1.zendapi.printing.zend-printf">
<title><function>zend_printf</function></title>
<para>
<function>zend_printf</function> works like the
standard <function>printf</function>, except that it prints to Zend's
output stream.
</para>
</sect3>
<sect3 xml:id="internals2.ze1.zendapi.printing.zend-error">
<title><function>zend_error</function></title>
<para>
<function>zend_error</function> can be used to generate error messages.
This function accepts two arguments; the first is the error type (see
<filename>zend_errors.h</filename>), and the second is the error message.
<programlisting role="c">
<![CDATA[
zend_error(E_WARNING, "This function has been called with empty arguments");
]]>
</programlisting>
<xref linkend="internals2.ze1.zendapi.tab.error-messages"/> shows a list
of possible values (see <link
linkend="internals2.ze1.zendapi.fig.warning-messages">below</link>). These
values are also referred to in <filename>php.ini</filename>. Depending on
which error type you choose, your messages will be logged.
<table xml:id="internals2.ze1.zendapi.tab.error-messages">
<title>Zend's Predefined Error Messages.</title>
<tgroup cols="2">
<colspec colnum="1" colname="col1" colwidth="1.00*"/>
<colspec colnum="2" colname="col2" colwidth="1.36*"/>
<tbody>
<row>
<entry colname="col1">Error</entry>
<entry colname="col2">Description</entry>
</row>
<row>
<entry colname="col1"><constant>E_ERROR</constant></entry>
<entry colname="col2">
Signals an error and terminates execution of the script
immediately.</entry>
</row>
<row>
<entry colname="col1"><constant>E_WARNING</constant></entry>
<entry colname="col2">
Signals a generic warning. Execution continues.
</entry>
</row>
<row>
<entry colname="col1"><constant>E_PARSE</constant></entry>
<entry colname="col2">
Signals a parser error. Execution continues.
</entry>
</row>
<row>
<entry colname="col1"><constant>E_NOTICE</constant></entry>
<entry colname="col2">
Signals a notice. Execution continues. Note that by
default the display of this type of error messages is turned off in
<filename>php.ini</filename>.
</entry>
</row>
<row>
<entry colname="col1"><constant>E_CORE_ERROR</constant></entry>
<entry colname="col2">
Internal error by the core; shouldn't be used by
user-written modules.
</entry>
</row>
<row>
<entry colname="col1"><constant>E_COMPILE_ERROR</constant></entry>
<entry colname="col2">
Internal error by the compiler; shouldn't be used by
user-written modules.
</entry>
</row>
<row>
<entry colname="col1"><constant>E_COMPILE_WARNING</constant></entry>
<entry colname="col2">
Internal warning by the compiler; shouldn't be used by
user-written modules.
</entry>
</row>
</tbody>
</tgroup>
</table>
<mediaobject xml:id="internals2.ze1.zendapi.fig.warning-messages">
<alt>Display of warning messages in the browser.</alt>
<imageobject>
<imagedata fileref="en/internals2/ze1/zendapi/figures/zend.07-warning-messages.png"/>
</imageobject>
</mediaobject>
</para>
</sect3>
<sect3 xml:id="internals2.ze1.zendapi.printing.phpinfo">
<title>Including Output in <function>phpinfo</function></title>
<para>
After creating a real module, you'll want to show information
about the module in <function>phpinfo</function> (in addition to the
module name, which appears in the module list by default). PHP allows
you to create your own section in the <function>phpinfo</function> output with the <literal>ZEND_MINFO()</literal> function. This function
should be placed in the module descriptor block (discussed earlier) and is
always called whenever a script calls <function>phpinfo</function>.
</para>
<para>
PHP automatically prints a section
in <function>phpinfo</function> for you if you specify the <literal>ZEND_MINFO</literal>
function, including the module name in the heading. Everything else must be
formatted and printed by you.
</para>
<para>
Typically, you can print an HTML table header
using <function>php_info_print_table_start</function> and then use the standard
functions <function>php_info_print_table_header</function>
and <function>php_info_print_table_row</function>. As arguments, both take the number of
columns (as integers) and the column contents (as strings). <xref linkend="internals2.ze1.zendapi.example.phpinfo"/> shows a source example and its output. To print the table footer, use <function>php_info_print_table_end</function>.
</para>
<example xml:id="internals2.ze1.zendapi.example.phpinfo">
<title>
Source code and screenshot for output in <function>phpinfo</function>.
</title>
<programlisting role="c">
<![CDATA[
php_info_print_table_start();
php_info_print_table_header(2, "First column", "Second column");
php_info_print_table_row(2, "Entry in first row", "Another entry");
php_info_print_table_row(2, "Just to fill", "another row here");
php_info_print_table_end();
]]>
</programlisting>
<mediaobject>
<alt>Output of phpinfo()</alt>
<imageobject>
<imagedata fileref="en/internals2/ze1/zendapi/figures/zend.08-phpinfo-output.png"/>
</imageobject>
</mediaobject>
</example>
</sect3>
<sect3 xml:id="internals2.ze1.zendapi.printing.execution">
<title>Execution Information</title>
<para>
You can also print execution information, such as the current file
being executed. The name of the function currently being executed
can be retrieved using the function
<function>get_active_function_name</function>. This function
returns a pointer to the function name and doesn't accept any
arguments. To retrieve the name of the file currently being
executed, use <function>zend_get_executed_filename</function>.
This function accesses the executor globals, which are passed to
it using the <literal>TSRMLS_C</literal> macro. The executor globals
are automatically available to every function that's called
directly by Zend (they're part of the
<literal>INTERNAL_FUNCTION_PARAMETERS</literal> described earlier
in this chapter). If you want to access the executor globals in
another function that doesn't have them available automatically,
call the macro <literal>TSRMLS_FETCH()</literal> once in that
function; this will introduce them to your local scope.
</para>
<para>
Finally, the line number currently being executed can be retrieved
using the function <function>zend_get_executed_lineno</function>.
This function also requires the executor globals as arguments. For
examples of these functions, see <xref linkend="internals2.ze1.zendapi.example.exec-info"/>.
</para>
<example xml:id="internals2.ze1.zendapi.example.exec-info">
<title>Printing execution information.</title>
<programlisting role="c">
<![CDATA[
zend_printf("The name of the current function is %s<br>", get_active_function_name(TSRMLS_C));
zend_printf("The file currently executed is %s<br>", zend_get_executed_filename(TSRMLS_C));
zend_printf("The current line being executed is %i<br>", zend_get_executed_lineno(TSRMLS_C));
]]>
</programlisting>
<mediaobject>
<alt>Printing execution information</alt>
<imageobject>
<imagedata fileref="en/internals2/ze1/zendapi/figures/zend.09-execution-info.png"/>
</imageobject>
</mediaobject>
</example>
</sect3>
</sect2>
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