There are several types of errors and warnings in PHP. They are:
Table 15-1. PHP error types
| Value |
Constant |
Description |
Note |
| 1 |
E_ERROR |
fatal run-time errors |
|
| 2 |
E_WARNING |
run-time warnings (non fatal errors) |
|
| 4 |
E_PARSE |
compile-time parse errors |
|
| 8 |
E_NOTICE |
run-time notices (less serious than warnings) |
|
| 16 |
E_CORE_ERROR |
fatal errors that occur during PHP's initial startup |
PHP 4 only |
| 32 |
E_CORE_WARNING |
warnings (non fatal errors) that occur during PHP's initial
startup |
PHP 4 only |
| 64 |
E_COMPILE_ERROR |
fatal compile-time errors |
PHP 4 only |
| 128 |
E_COMPILE_WARNING |
compile-time warnings (non fatal errors) |
PHP 4 only |
| 256 |
E_USER_ERROR |
user-generated error message |
PHP 4 only |
| 512 |
E_USER_WARNING |
user-generated warning message |
PHP 4 only |
| 1024 |
E_USER_NOTICE |
user-generated notice message |
PHP 4 only |
| |
E_ALL |
all of the above, as supported |
|
The above values (either numerical or symbolic) are used to build up a bitmask that
specifies which errors to report. You can use the bitwise
operators to combine these values or mask out certain types of errors. Note that only '|', '~',
'!', and '∓' will be understood within php.ini, however, and that no bitwise operators
will be understood within php3.ini.
In PHP 4, the default error_reporting
setting is E_ALL ∓ ~E_NOTICE, meaning to display all errors and warnings which are not
E_NOTICE-level. In PHP 3, the default setting is (E_ERROR | E_WARNING | E_PARSE), meaning
the same thing. Note, however, that since constants are not supported in PHP 3's php3.ini,
the error_reporting setting there must be
numeric; hence, it is 7.
The initial setting can be changed in the ini file with the error_reporting directive, in your Apache
httpd.conf file with the php_error_reporting (php3_error_reporting for PHP 3) directive, and
lastly it may be set at runtime within a script by using the error_reporting() function.
| Warning |
|
When upgrading code or servers from PHP 3 to PHP 4 you should check these settings and
calls to error_reporting() or you might disable
reporting the new error types, especially E_COMPILE_ERROR. This may lead to empty documents without
any feedback of what happened or where to look for the problem.
|
All PHP expressions can also be called with the
"@" prefix, which turns off error reporting for that particular expression. If an error occurred
during such an expression and the track_errors
feature is enabled, you can find the error message in the global variable
$php_errormsg.
Note: The @ error-control operator
prefix will not disable messages that are the result of parse errors.
| Warning |
|
Currently the @ error-control operator
prefix will even disable error reporting for critical errors that will terminate script execution.
Among other things, this means that if you use @
to suppress errors from a certain function and either it isn't available or has been mistyped, the
script will die right there with no indication as to why.
|
Below we can see an example of using the error handling capabilities in PHP. We define a
error handling function which logs the information into a file (using an XML format), and e-mails
the developer in case a critical error in the logic happens.
|
Example 15-1. Using error handling in a script
<?php
// we will do our own error handling
error_reporting(0);
// user defined error handling function
function userErrorHandler ($errno, $errmsg, $filename, $linenum, $vars) {
// timestamp for the error entry
$dt = date("Y-m-d H:i:s (T)");
// define an assoc array of error string
// in reality the only entries we should
// consider are 2,8,256,512 and 1024
$errortype = array (
1 => "Error",
2 => "Warning",
4 => "Parsing Error",
8 => "Notice",
16 => "Core Error",
32 => "Core Warning",
64 => "Compile Error",
128 => "Compile Warning",
256 => "User Error",
512 => "User Warning",
1024=> "User Notice"
);
// set of errors for which a var trace will be saved
$user_errors = array(E_USER_ERROR, E_USER_WARNING, E_USER_NOTICE);
$err = "<errorentry>\n";
$err .= "\t<datetime>".$dt."</datetime>\n";
$err .= "\t<errornum>".$errno."</errornum>\n";
$err .= "\t<errortype>".$errortype[$errno]."</errortype>\n";
$err .= "\t<errormsg>".$errmsg."</errormsg>\n";
$err .= "\t<scriptname>".$filename."</scriptname>\n";
$err .= "\t<scriptlinenum>".$linenum."</scriptlinenum>\n";
if (in_array($errno, $user_errors))
$err .= "\t<vartrace>".wddx_serialize_value($vars,"Variables")."</vartrace>\n";
$err .= "</errorentry>\n\n";
// for testing
// echo $err;
// save to the error log, and e-mail me if there is a critical user error
error_log($err, 3, "/usr/local/php4/error.log");
if ($errno == E_USER_ERROR)
mail("phpdev@mydomain.com","Critical User Error",$err);
}
function distance ($vect1, $vect2) {
if (!is_array($vect1) || !is_array($vect2)) {
trigger_error("Incorrect parameters, arrays expected", E_USER_ERROR);
return NULL;
}
if (count($vect1) != count($vect2)) {
trigger_error("Vectors need to be of the same size", E_USER_ERROR);
return NULL;
}
for ($i=0; $i<count($vect1); $i++) {
$c1 = $vect1[$i]; $c2 = $vect2[$i];
$d = 0.0;
if (!is_numeric($c1)) {
trigger_error("Coordinate $i in vector 1 is not a number, using zero",
E_USER_WARNING);
$c1 = 0.0;
}
if (!is_numeric($c2)) {
trigger_error("Coordinate $i in vector 2 is not a number, using zero",
E_USER_WARNING);
$c2 = 0.0;
}
$d += $c2*$c2 - $c1*$c1;
}
return sqrt($d);
}
$old_error_handler = set_error_handler("userErrorHandler");
// undefined constant, generates a warning
$t = I_AM_NOT_DEFINED;
// define some "vectors"
$a = array(2,3,"foo");
$b = array(5.5, 4.3, -1.6);
$c = array (1,-3);
// generate a user error
$t1 = distance($c,$b)."\n";
// generate another user error
$t2 = distance($b,"i am not an array")."\n";
// generate a warning
$t3 = distance($a,$b)."\n";
?>
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This is just a simple example showing how to use the Error Handling
and Logging functions.
See also error_reporting(), error_log(),
set_error_handler(),
restore_error_handler(), trigger_error(),
user_error()
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