PEAR Reference ManualPEAR
This chapter contains reference documentation for PEAR components
that are distributed with PHP. It is assumed that you are
already familiar with objects and
classes.
PEARPEAR base classrequire_once "PEAR.php";class classname extends PEAR { ... }Description
The PEAR base class provides standard functionality that is used
by most PEAR classes. Normally you never make an instance of the
PEAR class directly, you use it by subclassing it.
Its key features are:
request-shutdown object "destructors"error handlingPEAR "destructors"
If you inherit PEAR in a class called
ClassName, you can define a method in
it called called _ClassName (the
class name with an underscore prepended) that will be invoked
when the request is over. This is not a destructor in the sense
that you can "delete" an object and have the destructor called,
but in the sense that PHP gives you a callback in the object
when it is done executing. See the example below.
PEAR Error Handling
PEAR's base class also provides a way of passing around more
complex errors than a &true;/false value or a numeric code. A
PEAR error is an object that is either an instance of the class
PEAR_Error, or some class inheriting
PEAR_Error.
One of the design criteria of PEAR's errors is that it should
not force a particular type of output on the user, it should be
possible to handle errors without any output at all if that is
desireable. This makes it possible to handle errors gracefully,
also when your output format is different from HTML (for example
WML or some other XML format).
The error object can be configured to do a number of things when
it is created, such as printing an error message, printing the
message and exiting, raising an error with PHP's
trigger_error function, invoke a callback,
or none of the above. This is typically specified in
PEAR_Error's constructor, but all of the
parameters are optional, and you can set up defaults for errors
generated from each object based on the
PEAR class. See the PEAR error examples for how
to use it and the PEAR_Error reference
for the full details.
Examples
The example below shows how to use the PEAR's "poor man's kinda
emulated destructors" to implement a simple class that holds the
contents of a file, lets you append data to the object and
flushes the data back to the file at the end of the request:
PEAR: emulated destructors
require_once "PEAR.php";
class FileContainer extends PEAR
{
var $file = '';
var $contents = '';
var $modified = 0;
function FileContainer($file)
{
$this->PEAR(); // this calls the parent class constructor
$fp = fopen($file, "r");
if (!is_resource($fp)) {
return;
}
while (!empty($data = fread($fp, 2048))) {
$this->contents .= $data;
}
fclose($fp);
}
function append($str)
{
$this->contents .= $str;
$this->modified++;
}
// The "destructor" is named like the constructor
// but with an underscore in front.
function _FileContainer()
{
if ($this->modified) {
$fp = fopen($this->file, "w");
if (!is_resource($fp)) {
return;
}
fwrite($fp, $this->contents);
fclose($fp);
}
}
}
$fileobj = new FileContainer("testfile");
$fileobj->append("this ends up at the end of the file\n");
// When the request is done and PHP shuts down, $fileobj's
// "destructor" is called and updates the file on disk.
PEAR "destructors" use PHP's shutdown callbacks
(register_shutdown_function), and you
can't output anything from these when PHP is running in a web
server. So anything printed in a "destructor" gets lost except
when PHP is used in command-line mode. Bummer.
The next examples illustrate different ways of using PEAR's error
handling mechanism.
PEAR error example (1)
function mysockopen($host = "localhost", $port = 8090)
{
$fp = fsockopen($host, $port, $errno, $errstr);
if (!is_resource($fp)) {
return new PEAR_Error($errstr, $errno);
}
return $fp;
}
$sock = mysockopen();
if (PEAR::isError($sock)) {
print "mysockopen error: ".$sock->getMessage()."<BR>\n"
}
This example shows a wrapper to fsockopen
that delivers the error code and message (if any) returned by
fsockopen in a PEAR error object. Notice that
PEAR::isError is used to detect whether a
value is a PEAR error.
PEAR_Error's mode of operation in this example is simply
returning the error object and leaving the rest to the user
(programmer). This is the default error mode.
In the next example we're showing how to use default error modes:
PEAR error example (2)
class TCP_Socket extends PEAR
{
var $sock;
function TCP_Socket()
{
$this->PEAR();
}
function connect($host, $port)
{
$sock = fsockopen($host, $port, $errno, $errstr);
if (!is_resource($sock)) {
return $this->raiseError($errstr, $errno);
}
}
}
$sock = new TCP_Socket;
$sock->setErrorHandling(PEAR_ERROR_DIE);
$sock->connect("localhost", 8090);
print "still alive<BR>\n";
Here, we set the default error mode to
PEAR_ERROR_DIE, and since we don't specify
any error mode in the raiseError call (that'd be the third
parameter), raiseError uses the default error mode and exits if
fsockopen fails.
PEAR_ErrorPEAR error mechanism base class$err = new PEAR_Error($msg);Error Modes
An error object has a mode of operation that can be set with one
of the following constants:
PEAR_ERROR_RETURN
Just return the object, don't do anything special in
PEAR_Error's constructor.
PEAR_ERROR_PRINT
Print the error message in the constructor. The execution is
not interrupted.
PEAR_ERROR_TRIGGER
Use PHP's trigger_error function to
raise an internal error in PHP. The execution is aborted if
you have defined your own PHP error handler or if you set the
error severity to E_USER_ERROR.
PEAR_ERROR_DIE
Print the error message and exit. Execution is of course
aborted.
PEAR_ERROR_CALLBACK
Use a callback function or method to handle errors.
Execution is aborted.
PropertiesMethodsPEAR_Error::PEAR_ErrormessagecodemodeoptionsuserinfoDescription
PEAR_Error constructor. Parameters:
message
error message, defaults to "unknown error"
code
error code (optional)
mode
Mode of operation. See the error modes section for
details.
options
If the mode of can have any options specified, use this
parameter. Currently the "trigger" and "callback" modes are
the only using the options parameter. For trigger mode,
this parameter is one of E_USER_NOTICE,
E_USER_WARNING or
E_USER_ERROR. For callback mode, this
parameter should contain either the callback function name
(string), or a two-element (object, string) array
representing an object and a method name.