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8.18. Logging Errors
8.18.1. Problem
You want to write program errors to a log. These errors can include everything from parser errors and files not being found to bad database queries and dropped connections.
8.18.2. Solution
Use error_log( ) to write to the error log:
// LDAP error
if (ldap_errno($ldap)) {
error_log("LDAP Error #" . ldap_errno($ldap) . ": " . ldap_error($ldap));
}8.18.3. Discussion
Logging errors facilitates debugging. Smart error logging makes it easier to fix bugs. Always log information about what caused the error:
$r = mysql_query($sql);
if (! $r) {
$error = mysql_error( );
error_log('[DB: query @'.$_SERVER['REQUEST_URI']."][$sql]: $error");
} else {
// process results
}You're not getting all the debugging help you could be if you simply log that an error occurred without any supporting information:
$r = mysql_query($sql);
if (! $r) {
error_log("bad query");
} else {
// process result
}Another useful technique is to include the _ _FILE_ _ and _ _LINE_ _ constants in your error messages:
error_log('['._ _FILE_ _.']['._ _LINE_ _."]: $error");The _ _FILE_ _ constant is the current filename, and _ _LINE_ _ is the current line number.
8.18.4. See Also
Recipe 8.15 for hiding error messages from users; documentation on error_log( ) at http://www.php.net/error-log.
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| 8.17. Using a Custom Error Handler |  | 8.19. Eliminating "headers already sent" Errors |
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