PHP 7.0.0 Beta 2 Released

goto

(PHP 5 >= 5.3.0)

Quelle est la chose la plus bizarre lors de l'utilisation de goto ?
Image fournie par » xkcd

L'opérateur goto peut être utilisé pour continuer l'exécution du script à un autre point du programme. La cible est spécifiée par un label, suivi de deux-point, et l'instruction goto est ensuite suivie de ce label. goto n'est pas totalement sans limitations. L'étiquette cible doit être dans le même contexte et fichier, ce qui signifie qu'il n'est pas possible de changer de méthode ou de fonction, ni de se rendre dans une autre fonction. Vous pouvez sortir d'une fonction, et l'utilisation courante est alors de se servir de goto comme un break.

Exemple #1 Exemple avec goto

<?php
goto a;
echo 
'Foo';
 
a:
echo 
'Bar';
?>

L'exemple ci-dessus va afficher :

Bar

Exemple #2 Exemple de boucle avec goto

<?php
for($i=0,$j=50$i<100$i++) {
  while(
$j--) {
    if(
$j==17) goto end
  }  
}
echo 
"i = $i";
end:
echo 
'j hit 17';
?>

L'exemple ci-dessus va afficher :

j hit 17

Exemple #3 Ce goto ne fonctionne pas

<?php
goto loop;
for(
$i=0,$j=50$i<100$i++) {
  while(
$j--) {
    
loop:
  }
}
echo 
"$i = $i";
?>

L'exemple ci-dessus va afficher :

Fatal error: 'goto' into loop or switch statement is disallowed in
script on line 2

Note:

L'opérateur goto est disponible depuis PHP 5.3.

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User Contributed Notes 6 notes

up
27
chrisstocktonaz at gmail dot com
5 years ago
Remember if you are not a fan of wild labels hanging around you are free to use braces in this construct creating a slightly cleaner look. Labels also are always executed and do not need to be called to have their associated code block ran. A purposeless example is below.

<?php

$headers
= Array('subject', 'bcc', 'to', 'cc', 'date', 'sender');
$position = 0;

hIterator: {

   
$c = 0;
    echo
$headers[$position] . PHP_EOL;

   
cIterator: {
        echo
' ' . $headers[$position][$c] . PHP_EOL;

        if(!isset(
$headers[$position][++$c])) {
            goto
cIteratorExit;
        }
        goto
cIterator;
    }

   
cIteratorExit: {
        if(isset(
$headers[++$position])) {
            goto
hIterator;
        }
    }
}
?>
up
25
Ray dot Paseur at Gmail dot com
3 years ago
You cannot implement a Fortran-style "computed GOTO" in PHP because the label cannot be a variable. See: http://en.wikipedia.org/wiki/Considered_harmful

<?php // RAY_goto.php
error_reporting(E_ALL);

// DEMONSTRATE THAT THE GOTO LABEL IS CASE-SENSITIVE

goto a;
echo
'Foo';
a: echo 'Bar';

goto
A;
echo
'Foo';
A: echo 'Baz';

// CAN THE GOTO LABEL BE A VARIABLE?

$a = 'abc';
goto
$a; // NOPE: PARSE ERROR
echo 'Foo';
abc: echo 'Boom';
?>
up
6
sixoclockish at gmail dot com
3 years ago
You are also allowed to jump backwards with a goto statement. To run a block of goto as one block is as follows:
example has a prefix of iw_ to keep label groups structured and an extra underscore to do a backwards goto.

Note the `iw_end_gt` to get out of the labels area

<?php
    $link
= true;

    if (
$link ) goto iw_link_begin;
    if(
false) iw__link_begin:
   
    if (
$link ) goto iw_link_text;
    if(
false) iw__link_text:
   
    if (
$link ) goto iw_link_end;
    if(
false) iw__link_end:
   
    goto
iw_end_gt;
   
   
    if (
false) iw_link_begin:
        echo
'<a href="#">';
    goto
iw__link_begin;
   
    if (
false) iw_link_text:
        echo
'Sample Text';
    goto
iw__link_text;
   
    if (
false) iw_link_end:
        echo
'</a>';
    goto
iw__link_end;
   
   
iw_end_gt:
?>
up
5
f at francislacroix dot info
3 years ago
The goto operator CAN be evaluated with eval, provided the label is in the eval'd code:

<?php
a
: eval("goto a;"); // undefined label 'a'
eval("a: goto a;"); // works
?>

It's because PHP does not consider the eval'd code, containing the label, to be in the same "file" as the goto statement.
up
0
ryan DOT jentzsch AT NOSPAM [G]mail com
3 months ago
Like the eval() function; if GOTO is the answer then you are definitely asking the wrong question.
GOTO is the daredevil of all programming languages. Like Evil Knievel the GOTO can jump from one place in your code to a completely different place with no return.
Knievel broke nearly every bone in his body making his jumps. GOTO will absolutely break your apps bones.
Google "Spaghetti code" for how GOTO is used. Like the eval() function; if GOTO is the answer then you are definitely asking the wrong question.
GOTO is the daredevil of all programming languages. Like Evil Knievel the GOTO can jump from one place in your code to a completely different place with no return.
Knievel broke nearly every bone in his body making his jumps. GOTO will absolutely break your apps bones.
Google "Spaghetti code" for how GOTO is used.
up
-27
fff at hotmail dot com
5 months ago
goto is actually really sweet once you learn to use it correctly, it will give you a smaller object in the end, and less ascii code. Those who dont know what instruction the goto statement will be parsed into should probably stay away :P
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