异常

目录

PHP 有一个和其他语言相似的异常模型。 在 PHP 里可以 throwcatch 异常。 为了捕获潜在的异常,可以将代码包含在 try 块里。 每个 try 都必须有一个相应的 catchfinally 代码块。

如果抛出异常的函数范围内没有 catch 块,异常会沿调用栈“向上冒泡”, 直到找到匹配的 catch 块。 沿途会执行所有遇到的 finally 块。 在没有设置全局异常处理程序(exception handler)时, 如果调用栈向上都没有遇到匹配的 catch,程序会抛出 fatal 错误并终止执行。

抛出的对象必须是 Exception 自身或 Exception的子类。 抛出其他对象会导致 PHP 报 Fatal 错误。

PHP 8.0.0 起,throw 关键词现在开始是一个表达式,可用于任何表达式的场景。 在此之前,它是一个语句,必须独占一行。

catch

catch 定义了处理抛出异常的方式。 catch 块定义了它能处理的异常/错误的类型,并可以选择将异常赋值到变量中。 (在 PHP 8.0.0 之前的版本中必须要赋值到变量) 如果遇到抛出对象的类型匹配了首个 catch 块的异常或错误,将会处理该对象。

可用多个 catch 捕获不同的异常类。 正常情况下(try 代码块里没有抛出异常)会在最后一个定义的 catch 后面继续执行。 catch 代码块里也可以 throw 或者重新抛出异常。 不抛出的话,会在触发的 catch 后面继续执行。

当 PHP 抛出一个异常时,将不会执行后续的代码语句,并会尝试查找首个匹配的 catch 代码块。 如果没有用 set_exception_handler() 设置异常处理函数, PHP 会在异常未被捕获时产生 Fatal 级错误,提示 "Uncaught Exception ..." 消息。

从 PHP 7.1.0 起 catch 可以用竖线符(|) 指定多个异常。 如果在不同的类层次结构中,不同异常的异常需要用同样的方式处理,就特别适用这种方式。

从 PHP 8.0.0 起,捕获的异常不再强制要求指定变量名。 catch 代码块会在未指定时继续执行,只是无法访问到抛出的对象。

finally

finally 代码块可以放在 catch 之后,或者直接代替它。 无论是否抛出了异常,在 trycatch 之后、在执行后续代码之前, 放在 finally 里的代码总是会执行。

值得注意的是 finallyreturn 语句之间存在相互影响。 如果在 trycatch 里遇到 return,仍然会执行 finally 里的代码。 而且,遇到 return 语句时,会先执行 finally 再返回结果。 此外,如果 finally 里也包含了 return 语句,将返回 finally 里的值。

全局异常处理器

当允许异常冒泡到全局范围时,它可以被全局异常处理器捕获到。 set_exception_handler() 可以设置一个函数,在没有调用其他块时代替 catch。 在本质上,实现的效果等同于整个程序被 try-catch 包裹起来, 而该函数就是 catch

注释

注意:

PHP 内部函数主要使用 错误报告, 只有一些现代 面向对象 的扩展使用异常。 不过,错误很容易用 ErrorException 转化成异常。 然而,这个技术方案仅适用非 Fatal 级的错误。

示例 #3 将错误报告转成异常

<?php
function exceptions_error_handler($severity$message$filename$lineno) {
    throw new 
ErrorException($message0$severity$filename$lineno);
}

set_error_handler('exceptions_error_handler');
?>

小技巧

PHP 标准库(SPL) 提供了大量的 标准内置异常

范例

示例 #4 抛出一个异常

<?php
function inverse($x) {
    if (!
$x) {
        throw new 
Exception('Division by zero.');
    }
    return 
1/$x;
}

try {
    echo 
inverse(5) . "\n";
    echo 
inverse(0) . "\n";
} catch (
Exception $e) {
    echo 
'Caught exception: ',  $e->getMessage(), "\n";
}

// Continue execution
echo "Hello World\n";
?>

以上例程会输出:

0.2
Caught exception: Division by zero.
Hello World

示例 #5 带 finally 块的异常处理

<?php
function inverse($x) {
    if (!
$x) {
        throw new 
Exception('Division by zero.');
    }
    return 
1/$x;
}

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

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

// 继续执行
echo "Hello World\n";
?>

以上例程会输出:

0.2
First finally.
Caught exception: Division by zero.
Second finally.
Hello World

示例 #6 finallyreturn 相互之间的影响

<?php

function test() {
    try {
        throw new 
Exception('foo');
    } catch (
Exception $e) {
        return 
'catch';
    } finally {
        return 
'finally';
    }
}

echo 
test();
?>

以上例程会输出:

finally

示例 #7 异常嵌套

<?php

class MyException extends Exception { }

class 
Test {
    public function 
testing() {
        try {
            try {
                throw new 
MyException('foo!');
            } catch (
MyException $e) {
                
// 重新 throw
                
throw $e;
            }
        } catch (
Exception $e) {
            
var_dump($e->getMessage());
        }
    }
}

$foo = new Test;
$foo->testing();

?>

以上例程会输出:

string(4) "foo!"

示例 #8 多个异常的捕获处理

<?php

class MyException extends Exception { }

class 
MyOtherException extends Exception { }

class 
Test {
    public function 
testing() {
        try {
            throw new 
MyException();
        } catch (
MyException MyOtherException $e) {
            
var_dump(get_class($e));
        }
    }
}

$foo = new Test;
$foo->testing();

?>

以上例程会输出:

string(11) "MyException"

示例 #9 忽略捕获的变量

仅仅在 PHP 8.0.0 及以上版本有效

<?php

class SpecificException extends Exception {}

function 
test() {
    throw new 
SpecificException('Oopsie');
}

try {
    
test();
} catch (
SpecificException) {
    print 
"A SpecificException was thrown, but we don't care about the details.";
}
?>

示例 #10 以表达式的形式抛出

仅仅在 PHP 8.0.0 及以上版本有效

<?php

class SpecificException extends Exception {}

function 
test() {
    
do_something_risky() or throw new Exception('It did not work');
}

try {
    
test();
} catch (
Exception $e) {
    print 
$e->getMessage();
}
?>
add a note add a note

User Contributed Notes 32 notes

up
300
zmunoz at gmail dot com
13 years ago
When catching an exception inside a namespace it is important that you escape to the global space:

<?php
namespace SomeNamespace;

class
SomeClass {

  function
SomeFunction() {
   try {
    throw new
Exception('Some Error Message');
   } catch (\
Exception $e) {
   
var_dump($e->getMessage());
   }
  }

}
?>
up
99
ohcc at 163 dot com
7 years ago
If a TRY has a FINALLY, a RETURN either in the TRY or a CATCH won't terminate the script. Code in the same block after the RETURN will not be executed, and the RETURN itself will be "copied" to the bottom of the FINALLY block to be executed.

a RETURN in the FINALLY block will override value(s) returned from the TRY or a CATCH block.

An EXIT or a DIE always terminate the script after themselves.

code 1

<?php
   
function foo(){
       
$bar = 1;
        try{
            throw new
Exception('I am Wu Xiancheng.');
        }catch(
Exception $e){
            return
$bar;
           
$bar--; // this line will be ignored
       
}finally{
           
$bar++;
        }
    }
    echo
foo(); // 2
?>

code 2

<?php
   
function foo(){
       
$bar = 1;
        try{
            throw new
Exception('I am Wu Xiancheng.');
        }catch(
Exception $e){
            return
$bar;
           
$bar--; // this line will be ignored
       
}finally{
           
$bar++;
            return
$bar;
        }
    }
    echo
foo(); //2
?>

code 3

<?php
   
function foo(){
       
$bar = 1;
        try{
            throw new
Exception('I am Wu Xiancheng.');
        }catch(
Exception $e){
            return
$bar;
           
$bar--; // this line will be ignored
       
}finally{
            return
100;
        }
    }
    echo
foo(); //100
?>
up
6
shaman_master at list dot ru
4 years ago
Example for PHP 7.0 or latest:
<?php
namespace SomeNamespace;

use
Throwable, Exception, Error;

class
SomeClass
{
    public function
someMethod()
    {
        try {
            if (
rand(0, 1)) {
                throw new
Exception('Some message');
            } else {
                throw new
Error('Some message');
            }
        } catch (
Throwable $e) {
            \
var_dump($e->getMessage());
        }
    }
   
    public function
__toString()
    {
        try {
            return (string)
$this->someMethod();
        } finally {
            return
'';
        }
    }
}
?>
up
81
ask at nilpo dot com
14 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}
up
2
David Spector
4 years ago
This page states, "Code may be surrounded in a try block, to facilitate the catching of potential exceptions." There are two ways in which code may be "surrounded". The obvious (intuitive) way is lexical enclosure: all the code to be protected by the try block is surrounded like this:

try
   {
   A();

   function A()
      {
      throw new Exception('error');
      echo "A()";
      } // A
   } // try
catch...

The other way to enclose is by execution (dynamic enclosure), like this:

try
   {
   A();
   } // try
catch...

function A()
   {
   throw new Exception('error');
   echo "A()";
   } // A

The sense in which code is "surrounded" for exception handling is dynamic (the second example above). This is because exception handling is dynamic and works by "unwinding" the execution stack.
up
9
christof+php[AT]insypro.com
6 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();
    }
?>
up
22
hweidmann at online dot de
8 years ago
catch doesn't check for the existence of the Exception class, so avoid typo.

<?php
  
class MyException extends Exception
  
{
      ...
   }

   try
   {
      throw new
MyException(...);
   }
   catch (
MuException $e) // <--- typo
  
{
      ...
   }
?>

You WON'T get
   Fatal error: Class MuException could not be loaded ...

You WILL get
   Fatal error: Uncaught exception 'MyException' ...
up
36
php at marcuspope dot com
10 years ago
Using a return statement inside a finally block will override any other return statement or thrown exception from the try block and all defined catch blocks.   Code execution in the parent stack will continue as if the exception was never thrown. 

Frankly this is a good design decision because it means I can optionally dismiss all thrown exceptions from 1 or more catch blocks in one place, without having to nest my whole try block inside an additional (and otherwise needless) try/catch block.

This is the same behavior as Java, whereas C# throws a compile time error when a return statement exists inside a finally block.  So I figured it was worth pointing out to PHP devs who may not have any exposure to finally blocks or how other languages do it.

<?php

function asdf()
{
    try {
        throw new
Exception('error');
    }
    catch(
Exception $e) {
        echo
"An error occurred";
        throw
$e;
    }
    finally {
               
//This overrides the exception as if it were never thrown
       
return "\nException erased";
    }
}

try {
    echo
asdf();
}
catch(
Exception $e) {
    echo
"\nResult: " . $e->getMessage();
}
?>

The output from above will look like this:

    An error occurred
    Exception erased

Without the return statement in the finally block it would look like this:

    An error occurred
    Result: error
up
67
Johan
12 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());
}
?>
up
13
ohcc at 163 dot com
8 years ago
Type declarations will trigger Uncaught TypeError when a different type is passed. And it cannot be caught with the Exception class.
<?php
   
function xc(array $a){       
    }   
    try{
       
xc(4);
    }catch (
Exception $e){ // failed to catch it
       
echo $e->getMessage();
    }
?>

You should use TypeError instead for PHP 7+,

<?php
   
function xc(array $a){   
    }   
    try{
       
xc(4);
    }catch (
TypeError $e){
        echo
$e->getMessage();
    }
?>

In php version prior to 7.0, you should translate Catchable fatal errors to an exception and then catch it.

<?php
   
function exceptionErrorHandler($errNumber, $errStr, $errFile, $errLine ) {
        throw new
ErrorException($errStr, 0, $errNumber, $errFile, $errLine);
    }
   
set_error_handler('exceptionErrorHandler');
    function
s(array $a){       
    }
    try{
       
s(4);
    }catch (
Exception $e){
        echo
$e->getMessage();
    }
?>
up
5
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 !"
up
20
jazfresh at hotmail.com
17 years ago
Sometimes you want a single catch() to catch multiple types of Exception. In a language like Python, you can specify multiple types in a catch(), but in PHP you can only specify one. This can be annoying when you want handle many different Exceptions with the same catch() block.

However, you can replicate the functionality somewhat, because catch(<classname> $var) will match the given <classname> *or any of it's sub-classes*.

For example:

<?php
class DisplayException extends Exception {};
class
FileException extends Exception {};
class
AccessControl extends FileException {}; // Sub-class of FileException
class IOError extends FileException {}; // Sub-class of FileException

try {
  if(!
is_readable($somefile))
     throw new
IOError("File is not readable!");
  if(!
user_has_access_to_file($someuser, $somefile))
     throw new
AccessControl("Permission denied!");
  if(!
display_file($somefile))
     throw new
DisplayException("Couldn't display file!");

} catch (
FileException $e) {
 
// This block will catch FileException, AccessControl or IOError exceptions, but not Exceptions or DisplayExceptions.
 
echo "File error: ".$e->getMessage();
  exit(
1);
}
?>

Corollary: If you want to catch *any* exception, no matter what the type, just use "catch(Exception $var)", because all exceptions are sub-classes of the built-in Exception.
up
4
jake at NOSPAM dot qzdesign dot co dot uk
6 years ago
Don't forget if your source file is in a namespace you will need to
<?php
use Throwable; // PHP 7
use Exception;
?>
or type the fully qualified class name (prefixed with `\`) as in
<?php
try {
 
// ...
} catch(\Throwable $e) {
 
// PHP 7
} catch(\Exception $e) {
 
// PHP 5
}
?>
otherwise you will only ever catch exceptions of the possibly non-existent classes `\YourNamespace\Throwable` and `\YourNamespace\Exception`!
up
13
jim at anderos dot com
10 years ago
If you are using a namespace, you must indicate the global namespace when using Exceptions.
<?php
namespace alpha;
function
foo(){
    throw new \
Exception("Something is wrong!");
   
// throw new Exception(""); will fail
}

try {
   
foo();
} catch( \
Exception $e ) {
   
// catch( Exception $e ) will give no warning, but will not catch Exception
   
echo "ERROR: $e";
}

?>
up
13
Shot (Piotr Szotkowski)
15 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).
up
17
sander at rotorsolutions dot nl
10 years ago
Just an example why finally blocks are usefull (5.5)

<?php

//without catch
function example() {
  try {
   
//do something that throws an exeption
 
}
  finally {
   
//this code will be executed even when the exception is executed
 
}
}

function
example2() {
  try {
    
//open sql connection check user as example
    
if(condition) {
        return
false;
     }
  }
  finally {
   
//close the sql connection, this will be executed even if the return is called.
 
}
}

?>
up
8
Simo
8 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.
up
15
Edu
10 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
up
7
telefoontoestel at nospam dot org
9 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
?>
up
7
cyrus+php at boadway dot ca
10 years ago
There's some inconsistent behaviour associated with PHP 5.5.3's finally and return statements. If a method returns a variable in a try block (e.g. return $foo;), and finally modifies that variable, the /modified/ value is returned. However, if the try block has a return that has to be evaluated in-line (e.g. return $foo+0;), finally's changes to $foo will /not/ affect the return value.

[code]
function returnVariable(){
    $foo = 1;
    try{
        return $foo;
    } finally {
        $foo++;
    }
}

function returnVariablePlusZero(){
    $foo = 1;
    try{
        return $foo + 0;
    } finally {
        $foo++;
    }
}

$test1 = returnVariable(); // returns 2, not the correct value of 1.
$test2 = returnVariablePlusZero(); // returns correct value of 1, but inconsistent with $test1.
[/code]

It looks like it's trying to be efficient by not allocating additional memory for the return value when it thinks it doesn't have to, but the spec is that finally is run after try is completed execution, and that includes the evaluation of the return expression.

One could argue (weakly) that the first method should be the correct result, but at least the two methods should be consistent.
up
4
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.
up
1
wisetips at gmail dot com
5 years ago
You should put your whole program into a try/catch block. Doing so is considered a best practice, because it will allow the user to continue to work even when there are errors in the page!
up
9
michael dot ochs at gmx dot net
16 years ago
Actually it isn't possible to do:
<?php
someFunction
() OR throw new Exception();
?>

This leads to a T_THROW Syntax Error. If you want to use this kind of exceptions, you can do the following:

<?php
function throwException($message = null,$code = null) {
    throw new
Exception($message,$code);
}

someFunction() OR throwException();
?>
up
1
Mohammad Hossein Darvishanpour
7 years ago
<?php
function Test_Extention($var1)
{
    if(
$var1 == false)
    {
        throw new
Exception('Invalid !');
    }
}
//end function

try
{
   
Test_Extention(false);
   
printf("%s","Valid");
}

catch(
Exception $e)
{
   
printf("%s","Message : " . $e->getMessage());
}
?>
up
3
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/>";
   }

?>
up
3
jon at hackcraft dot net
17 years ago
Further to dexen at google dot me dot up with "use destructors to perform a cleanup in case of exception". The fact that PHP5 has destructors, exception handling, and predictable garbage collection (if there's a single reference in scope and the scope is left then the destructor is called immediately) allows for the use of the RAII idiom.

http://en.wikipedia.org/wiki/Resource_Acquisition_Is_Initialization and my own http://www.hackcraft.net/RAII/ describe this.
up
0
daviddlowe dot flimm at gmail dot com
6 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 );
}

?>
up
0
fjoggen at gmail dot com
17 years ago
This code will turn php errors into exceptions:

<?php
function exceptions_error_handler($severity, $message, $filename, $lineno) {
    throw new
ErrorException($message, 0, $severity, $filename, $lineno);
}

set_error_handler('exceptions_error_handler');
?>

However since <?php set_error_handler()?> doesn't work with fatal errors, you will not be able to throw them as Exceptions.
up
-3
sander at rotorsolutions dot nl
10 years ago
Just an example why finally blocks are usefull (5.5)

<?php

//without catch
function example() {
  try {
   
//do something that throws an exeption
 
}
  finally {
   
//this code will be executed even when the exception is executed
 
}
}

function
example2() {
  try {
    
//open sql connection check user as example
    
if(condition) {
        return
false;
     }
  }
  finally {
   
//close the sql connection, this will be executed even if the return is called.
 
}
}
up
-9
alex dowgailenko [at] g mail . com
12 years ago
If you use the set_error_handler() to throw exceptions of errors, you may encounter issues with __autoload() functionality saying that your class doesn't exist and that's it.

If you do this:

<?php

class MyException extends Exception
{
}

class
Tester
{
    public function
foobar()
    {
        try
        {
           
$this->helloWorld();
        } catch (
MyException $e) {
            throw new
Exception('Problem in foobar',0,$e);
        }
    }
   
    protected function
helloWorld()
    {
        throw new
MyException('Problem in helloWorld()');
    }
}

$tester = new Tester;
try
{
   
$tester->foobar();
} catch (
Exception $e) {
    echo
$e->getTraceAsString();
}
?>

The trace will only show $tester->foobar() and not the call made to $tester->helloWorld().

In other words, if you pass a previous exception to a new one, the previous exception's stack trace is taken into account in the new exception.
up
-9
Hayley Watson
9 years ago
Remember that Exceptions are also objects and can be handled as such; they can be constructed in and returned as values from functions, passed as arguments to other functions, and examined before being thrown. You don't have to throw it as soon as you have constructed it (the stack trace will of course reflect the moment the Exception was constructed, not the moment it was thrown).

You might, for example, want to collect additional information to include in YourException but you don't want to clutter up the YourException class or the code containing the "throw" statement by collecting the information there. Or you might want to do something (such as logging) with each Exception that is thrown from a certain region (catch it, pass it to the logging function, then rethrow it).
up
-8
jenshausdorf at gmail dot com
6 years ago
Please don't do something like this:

<?php
try {
   
// experimental stuff to check whether something works
} catch(\Throwable $e) {
    return
false;
} finally {
    return
true;
}
?>

Well, it is allowed syntax, it is bad practice, because once it hits the exception block, finally won't be called(because it exits the scope). Finally was invented to prevent duplicated code after one operation, regardless whether it was successful(for example closing the connection to a server). This way, you don't have any duplicated code. So you don't need to use this structure.
To Top