Excepciones

Tabla de contenidos

Ampliar las Excepciones

PHP 5 tiene un modelo de excepciones similar al de otros lenguajes de programación. Una excepción puede ser lanzada ("thrown"), y atrapada ("catched") dentro de PHP. El código puede estar dentro de un bloque try para facilitar la captura de excepciones potenciales. Cada bloque try debe tener al menos un bloque catch o finally correspondiente.

El objeto lanzado debe ser una instancia de la clase Exception o una subclase de Exception. Intentar lanzar un objeto que no lo sea resultará en un Error Fatal de PHP.

`catch`

Se pueden usar múltiples bloques catch para atrapar diferentes clases de excepciones. La ejecución normal (cuando no es lanzada ninguna excepción dentro del bloque try) continuará después del último bloque catch definido en la sencuencia. Las excepciones pueden ser lanzadas ("thrown") (o relanzadas) dentro de un bloque catch.

Cuando una excepción es lanzada, el código siguiente a la declaración no será ejecutado, y PHP intentará encontrar el primer bloque catch coincidente. Si una excepción no es capturada, se emitirá un Error Fatal de PHP con un mensaje "Uncaught Exception ..." ("Excepción No Capturada"), a menos que se haya definido un manejador con set_exception_handler().

`finally`

En PHP 5.5 y posterior, se puede utilizar un bloque finally después o en lugar de los bloques catch. El código de dentro del bloque finally siempre se ejecutará después de los bloques try y catch, independientemente de que se haya lanzado una excepción o no, y antes de que la ejecución normal continúe.

Notas

Nota:
Las funciones internas de PHP utilizan principalmente la Información de Errores, sólo las extensiones Orientadas a objetos modernas utilizan excepciones. Sin embargo, los errores se pueden traducir a excepciones simplemente con ErrorException.

Sugerencia

La Biblioteca Estádar de PHP (SPL) proporciona un buen número de excepciones internas.

Ejemplos

Ejemplo #3 Lanzar una Excepción

<?php
function inverso($x) {
    if (!$x) {
        throw new Exception('División por cero.');
    }
    return 1/$x;
}

try {
    echo inverso(5) . "\n";
    echo inverso(0) . "\n";
} catch (Exception $e) {
    echo 'Excepción capturada: ',  $e->getMessage(), "\n";
}

// Continuar la ejecución
echo 'Hola Mundo\n';
?>

El resultado del ejemplo sería:

0.2
Excepción capturada: División por cero.
Hola Mundo

Ejemplo #4 Manejo de excepciones con un bloque finally

<?php
function inverse($x) {
    if (!$x) {
        throw new Exception('División por cero.');
    }
    return 1/$x;
}

try {
    echo inverse(5) . "\n";
} catch (Exception $e) {
    echo 'Excepción capturada: ',  $e->getMessage(), "\n";
} finally {
    echo "Primer finally.\n";
}

try {
    echo inverse(0) . "\n";
} catch (Exception $e) {
    echo 'Excepción capturada: ',  $e->getMessage(), "\n";
} finally {
    echo "Segundo finally.\n";
}

// Continuar ejecución
echo 'Hola Mundo\n';
?>

El resultado del ejemplo sería:

0.2
Primer finally.
Excepción capturada: División por cero.
Segundo finally.
Hola Mundo

Ejemplo #5 Excepciones anidadas

<?php

class MiExcepción extends Exception { }

class Prueba {
    public function probar() {
        try {
            try {
                throw new MiExcepción('foo!');
            } catch (MiExcepción $e) {
                // relanzarla
                throw $e;
            }
        } catch (Exception $e) {
            var_dump($e->getMessage());
        }
    }
}

$foo = new Prueba;
$foo->probar();

?>

El resultado del ejemplo sería:

string(4) "foo!"

Improve This Page

Learn How To Improve This Page • Submit a Pull Request • Report a Bug

＋add a note

User Contributed Notes 13 notes

down

125

ask at nilpo dot com ¶

15 years ago

If you intend on creating a lot of custom exceptions, you may find this code useful.  I've created an interface and an abstract exception class that ensures that all parts of the built-in Exception class are preserved in child classes.  It also properly pushes all information back to the parent constructor ensuring that nothing is lost.  This allows you to quickly create new exceptions on the fly.  It also overrides the default __toString method with a more thorough one.

<?php
interface IException
{
    /* Protected methods inherited from Exception class */
    public function getMessage();                 // Exception message 
    public function getCode();                    // User-defined Exception code
    public function getFile();                    // Source filename
    public function getLine();                    // Source line
    public function getTrace();                   // An array of the backtrace()
    public function getTraceAsString();           // Formated string of trace
    
    /* Overrideable methods inherited from Exception class */
    public function __toString();                 // formated string for display
    public function __construct($message = null, $code = 0);
}

abstract class CustomException extends Exception implements IException
{
    protected $message = 'Unknown exception';     // Exception message
    private   $string;                            // Unknown
    protected $code    = 0;                       // User-defined exception code
    protected $file;                              // Source filename of exception
    protected $line;                              // Source line of exception
    private   $trace;                             // Unknown

    public function __construct($message = null, $code = 0)
    {
        if (!$message) {
            throw new $this('Unknown '. get_class($this));
        }
        parent::__construct($message, $code);
    }
    
    public function __toString()
    {
        return get_class($this) . " '{$this->message}' in {$this->file}({$this->line})\n"
                                . "{$this->getTraceAsString()}";
    }
}
?>

Now you can create new exceptions in one line:

<?php
class TestException extends CustomException {}
?>

Here's a test that shows that all information is properly preserved throughout the backtrace.

<?php
function exceptionTest()
{
    try {
        throw new TestException();
    }
    catch (TestException $e) {
        echo "Caught TestException ('{$e->getMessage()}')\n{$e}\n";
    }
    catch (Exception $e) {
        echo "Caught Exception ('{$e->getMessage()}')\n{$e}\n";
    }
}

echo '<pre>' . exceptionTest() . '</pre>';
?>

Here's a sample output:

Caught TestException ('Unknown TestException')
TestException 'Unknown TestException' in C:\xampp\htdocs\CustomException\CustomException.php(31)
#0 C:\xampp\htdocs\CustomException\ExceptionTest.php(19): CustomException->__construct()
#1 C:\xampp\htdocs\CustomException\ExceptionTest.php(43): exceptionTest()
#2 {main}

down

tianyiw at vip dot qq dot com ¶

1 year ago

Easy to understand `finally`.
<?php
try {
    try {
        echo "before\n";
        1 / 0;
        echo "after\n";
    } finally {
        echo "finally\n";
    }
} catch (\Throwable) {
    echo "exception\n";
}
?>
# Print:
before
finally
exception

down

Johan ¶

13 years ago

Custom error handling on entire pages can avoid half rendered pages for the users:

<?php
ob_start();
try {
    /*contains all page logic 
    and throws error if needed*/
    ...
} catch (Exception $e) {
  ob_end_clean();
  displayErrorPage($e->getMessage());
}
?>

down

jlherren ¶

9 months ago

As noted elsewhere, throwing an exception from the `finally` block will replace a previously thrown exception. But the original exception is magically available from the new exception's `getPrevious()`.

<?php
try {
    try {
        throw new RuntimeException('Exception A');
    } finally {
        throw new RuntimeException('Exception B');
    }
}
catch (Throwable $exception) {
    echo $exception->getMessage(), "\n";
    // 'previous' is magically available!
    echo $exception->getPrevious()->getMessage(), "\n";
}
?>

Will print:

Exception B
Exception A

down

Shot (Piotr Szotkowski) ¶

16 years ago

‘Normal execution (when no exception is thrown within the try block, *or when a catch matching the thrown exception’s class is not present*) will continue after that last catch block defined in sequence.’

‘If an exception is not caught, a PHP Fatal Error will be issued with an “Uncaught Exception …” message, unless a handler has been defined with set_exception_handler().’

These two sentences seem a bit contradicting about what happens ‘when a catch matching the thrown exception’s class is not present’ (and the second sentence is actually correct).

down

christof+php[AT]insypro.com ¶

7 years ago

In case your E_WARNING type of errors aren't catchable with try/catch you can change them to another type of error like this:

<?php 
    set_error_handler(function($errno, $errstr, $errfile, $errline){
            if($errno === E_WARNING){
                // make it more serious than a warning so it can be caught
                trigger_error($errstr, E_ERROR);
                return true;
            } else {
                // fallback to default php error handler
                return false;
            }
    });

    try {
            // code that might result in a E_WARNING
    } catch(Exception $e){
            // code to handle the E_WARNING (it's actually changed to E_ERROR at this point)
    } finally {
            restore_error_handler();
    }
?>

down

daviddlowe dot flimm at gmail dot com ¶

7 years ago

Starting in PHP 7, the classes Exception and Error both implement the Throwable interface. This means, if you want to catch both Error instances and Exception instances, you should catch Throwable objects, like this:

<?php

try {
    throw new Error( "foobar" );
    // or:
    // throw new Exception( "foobar" );
}
catch (Throwable $e) {
    var_export( $e );
}

?>

down

Edu ¶

11 years ago

The "finally" block can change the exception that has been throw by the catch block.

<?php
try{
        try {
                throw new \Exception("Hello");
        } catch(\Exception $e) {
                echo $e->getMessage()." catch in\n";
                throw $e;
        } finally {
                echo $e->getMessage()." finally \n";
                throw new \Exception("Bye");
        }
} catch (\Exception $e) {
        echo $e->getMessage()." catch out\n";
}
?>

The output is:

Hello catch in
Hello finally 
Bye catch out

down

Simo ¶

9 years ago

#3 is not a good example. inverse("0a") would not be caught since (bool) "0a" returns true, yet 1/"0a" casts the string to integer zero and attempts to perform the calculation.

down

telefoontoestel at nospam dot org ¶

10 years ago

When using finally keep in mind that when a exit/die statement is used in the catch block it will NOT go through the finally block. 

<?php
try {
    echo "try block<br />";
    throw new Exception("test");
} catch (Exception $ex) {
    echo "catch block<br />";
} finally {
    echo "finally block<br />";
}

// try block
// catch block
// finally block
?>

<?php
try {
    echo "try block<br />";
    throw new Exception("test");
} catch (Exception $ex) {
    echo "catch block<br />";
    exit(1);
} finally {
    echo "finally block<br />";
}

// try block
// catch block
?>

down

mlaopane at gmail dot com ¶

6 years ago

<?php

/**
 * You can catch exceptions thrown in a deep level function
 */

function employee()
{
    throw new \Exception("I am just an employee !");
}

function manager()
{
    employee();
}

function boss()
{
    try {
        manager();
    } catch (\Exception $e) {
        echo $e->getMessage();
    }
}

boss(); // output: "I am just an employee !"

down

Tom Polomsk ¶

9 years ago

Contrary to the documentation it is possible in PHP 5.5 and higher use only try-finally blocks without any catch block.

down

Sawsan ¶

12 years ago

the following is an example of a re-thrown exception and the using of getPrevious function:

<?php

$name = "Name";

//check if the name contains only letters, and does not contain the word name

try
   {
   try
     {
      if (preg_match('/[^a-z]/i', $name)) 
       {
           throw new Exception("$name contains character other than a-z A-Z");
       }   
       if(strpos(strtolower($name), 'name') !== FALSE)
       {
          throw new Exception("$name contains the word name");
       }
       echo "The Name is valid";
     }
   catch(Exception $e)
     {
     throw new Exception("insert name again",0,$e);
     }
   }
 
catch (Exception $e)
   {
   if ($e->getPrevious())
   {
    echo "The Previous Exception is: ".$e->getPrevious()->getMessage()."<br/>";
   }
   echo "The Exception is: ".$e->getMessage()."<br/>";
   }

 ?>

＋add a note