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305 lines
10 KiB
XML
305 lines
10 KiB
XML
<chapter id="features.error-handling">
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<title>Error Handling</title>
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<para>
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There are several types of errors and warnings in PHP. They are:
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<table>
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<title>PHP error types</title>
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<tgroup cols="4">
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<thead>
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<row>
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<entry>Value</entry>
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<entry>Constant</entry>
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<entry>Description</entry>
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<entry>Note</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>1</entry>
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<entry>E_ERROR</entry>
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<entry>fatal run-time errors</entry>
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<entry></entry>
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</row>
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<row>
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<entry>2</entry>
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<entry>E_WARNING</entry>
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<entry>run-time warnings (non fatal errors)</entry>
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<entry></entry>
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</row>
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<row>
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<entry>4</entry>
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<entry>E_PARSE</entry>
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<entry>compile-time parse errors</entry>
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<entry></entry>
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</row>
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<row>
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<entry>8</entry>
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<entry>E_NOTICE </entry>
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<entry>
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run-time notices (less serious than warnings)
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</entry>
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<entry></entry>
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</row>
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<row>
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<entry>16</entry>
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<entry>E_CORE_ERROR</entry>
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<entry>fatal errors that occur during PHP's initial startup</entry>
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<entry>PHP 4 only</entry>
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</row>
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<row>
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<entry>32</entry>
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<entry>E_CORE_WARNING</entry>
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<entry>
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warnings (non fatal errors) that occur during PHP's initial
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startup
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</entry>
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<entry>PHP 4 only</entry>
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</row>
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<row>
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<entry>64</entry>
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<entry>E_COMPILE_ERROR</entry>
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<entry>fatal compile-time errors</entry>
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<entry>PHP 4 only</entry>
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</row>
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<row>
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<entry>128</entry>
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<entry>E_COMPILE_WARNING</entry>
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<entry>compile-time warnings (non fatal errors)</entry>
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<entry>PHP 4 only</entry>
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</row>
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<row>
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<entry>256</entry>
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<entry>E_USER_ERROR</entry>
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<entry>user-generated error message</entry>
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<entry>PHP 4 only</entry>
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</row>
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<row>
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<entry>512</entry>
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<entry>E_USER_WARNING</entry>
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<entry>user-generated warning message</entry>
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<entry>PHP 4 only</entry>
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</row>
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<row>
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<entry>1024</entry>
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<entry>E_USER_NOTICE </entry>
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<entry>user-generated notice message</entry>
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<entry>PHP 4 only</entry>
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</row>
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<row>
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<entry></entry>
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<entry>E_ALL</entry>
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<entry>all of the above, as supported</entry>
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<entry></entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</para>
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<para>
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The above values (either numerical or symbolic) are used to build
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up a bitmask that specifies which errors to report. You can use the
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<link linkend="language.operators.bitwise">bitwise operators</link>
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to combine these values or mask out certain types of errors. Note
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that only '|', '~', '!', and '&' will be understood within
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<filename>php.ini</filename>, however, and that no bitwise
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operators will be understood within <filename>php3.ini</filename>.
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</para>
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<para>
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In PHP 4, the default <link
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linkend="ini.error-reporting">error_reporting</link> setting is
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<literal>E_ALL & ~E_NOTICE</literal>, meaning to display all errors
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and warnings which are not E_NOTICE-level. In PHP 3, the default
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setting is <literal>(E_ERROR | E_WARNING | E_PARSE)</literal>,
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meaning the same thing. Note, however, that since constants are not
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supported in PHP 3's <filename>php3.ini</filename>, the <link
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linkend="ini.error-reporting">error_reporting</link> setting there
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must be numeric; hence, it is <literal>7</literal>.
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</para>
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<para>
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The initial setting can be changed in the ini file with the <link
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linkend="ini.error-reporting">error_reporting</link> directive, in
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your Apache <filename>httpd.conf</filename> file with the
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php_error_reporting (php3_error_reporting for PHP 3) directive, and
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lastly it may be set at runtime within a script by using the
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<function>error_reporting</function> function.
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</para>
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<warning>
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<para>
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When upgrading code or servers from PHP 3 to PHP 4 you should
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check these settings and calls to
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<function>error_reporting</function> or you might disable
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reporting the new error types, especially E_COMPILE_ERROR. This
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may lead to empty documents without any feedback of what happened
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or where to look for the problem.
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</para>
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</warning>
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<para>
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All <link linkend="language.expressions">PHP expressions</link> can
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also be called with the "@" prefix, which turns off error reporting
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for that particular expression. If an error occurred during such
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an expression and the <link
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linkend="ini.track-errors">track_errors</link> feature is enabled,
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you can find the error message in the global variable
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$php_errormsg.
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</para>
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<warning>
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<para>
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Currently the <link linkend="language.operators.errorcontrol">@
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error-control operator</link> prefix will even disable error
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reporting for critical errors that will terminate script
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execution. Among other things, this means that if you use <link
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linkend="language.operators.errorcontrol">@</link> to suppress
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errors from a certain function and either it isn't available or
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has been mistyped, the script will die right there with no
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indication as to why.
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</para>
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</warning>
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<para>
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Below we can see an example of using the error handling capabilities in
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PHP. We define a error handling function which logs the information into
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a file (using an XML format), and e-mails the developer in case a critical
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error in the logic happens.
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<example>
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<title>Using error handling in a script</title>
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<programlisting role="php">
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<?php
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// we will do our own error handling
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error_reporting(0);
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// user defined error handling function
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function userErrorHandler ($errno, $errmsg, $filename, $linenum, $vars) {
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// timestamp for the error entry
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$dt = date("Y-m-d H:i:s (T)");
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// define an assoc array of error string
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// in reality the only entries we should
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// consider are 2,8,256,512 and 1024
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$errortype = array (
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1 => "Error",
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2 => "Warning",
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4 => "Parsing Error",
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8 => "Notice",
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16 => "Core Error",
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32 => "Core Warning",
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64 => "Compile Error",
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128 => "Compile Warning",
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256 => "User Error",
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512 => "User Warning",
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1024=> "User Notice"
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);
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// set of errors for which a var trace will be saved
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$user_errors = array(E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE);
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$err = "<errorentry>\n";
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$err .= "\t<datetime>".$dt."</datetime>\n";
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$err .= "\t<errornum>".$errno."</errnumber>\n";
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$err .= "\t<errortype>".$errortype[$errno]."</errortype>\n";
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$err .= "\t<errormsg>".$errmsg."</errormsg>\n";
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$err .= "\t<scriptname>".$filename."</scriptname>\n";
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$err .= "\t<scriptlinenum>".$linenum."</scriptlinenum>\n";
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if (in_array($errno, $user_errors))
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$err .= "\t<vartrace>".wddx_serialize_value($vars,"Variables")."</vartrace>\n";
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$err .= "</errorentry>\n\n";
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// for testing
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// echo $err;
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// save to the error log, and e-mail me if there is a critical user error
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error_log($err, 3, "/usr/local/php4/error.log");
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if ($errno == E_USER_ERROR)
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mail("phpdev@mydomain.com","Critical User Error",$err);
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}
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function distance ($vect1, $vect2) {
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if (!is_array($vect1) || !is_array($vect2)) {
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trigger_error("Incorrect parameters, arrays expected", E_USER_ERROR);
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return NULL;
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}
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if (count($vect1) != count($vect2)) {
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trigger_error("Vectors need to be of the same size", E_USER_ERROR);
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return NULL;
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}
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for ($i=0; $i<count($vect1); $i++) {
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$c1 = $vect1[$i]; $c2 = $vect2[$i];
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$d = 0.0;
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if (!is_numeric($c1)) {
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trigger_error("Coordinate $i in vector 1 is not a number, using zero",
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E_USER_WARNING);
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$c1 = 0.0;
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}
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if (!is_numeric($c2)) {
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trigger_error("Coordinate $i in vector 2 is not a number, using zero",
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E_USER_WARNING);
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$c2 = 0.0;
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}
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$d += $c2*$c2 - $c1*$c1;
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}
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return sqrt($d);
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}
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$old_error_handler = set_error_handler("userErrorHandler");
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// undefined constant, generates a warning
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$t = I_AM_NOT_DEFINED;
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// define some "vectors"
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$a = array(2,3,"foo");
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$b = array(5.5, 4.3, -1.6);
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$c = array (1,-3);
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// generate a user error
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$t1 = distance($c,$b)."\n";
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// generate another user error
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$t2 = distance($b,"i am not an array")."\n";
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// generate a warning
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$t3 = distance($a,$b)."\n";
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?>
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</programlisting>
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</example>
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This is just a simple example showing how to use the
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<link linkend="ref.errorfunc">Error Handling and Logging
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functions</link>.
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</para>
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<para>
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See also <function>error_reporting</function>,
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<function>error_log</function>,
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<function>set_error_handler</function>,
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<function>restore_error_handler</function>,
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<function>trigger_error</function>,
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<function>user_error</function>
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</para>
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</chapter>
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Local variables:
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End:
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