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;
}
}
}
?>
goto
(PHP 5 >= 5.3.0, PHP 7)
goto 演算子を使用すると、 プログラム中の他の命令にジャンプすることができます。 ジャンプ先はラベルとコロンで表し、 goto の後にそのラベルを指定します。 これは、完全に制約のない goto というわけではありません。 対象となるラベルは同じファイル上の同じコンテキストになければなりません。 つまり、関数やメソッドの外に飛び出したり 関数やメソッドの中に突入したりすることはできないということです。 また、いかなるループや switch 構造の中にも突入することができません。 逆にループや switch 構造から抜け出すことはできます。一般的な用法としては、 goto を複数レベルの break として使うものがあります。
例1 goto の例
<?php
goto a;
echo 'Foo';
a:
echo 'Bar';
?>
上の例の出力は以下となります。
Bar
例2 ループでの goto の例
<?php
for($i=0,$j=50; $i<100; $i++) {
while($j--) {
if($j==17) goto end;
}
}
echo "i = $i";
end:
echo 'j hit 17';
?>
上の例の出力は以下となります。
j hit 17
例3 これは動作しません
<?php
goto loop;
for($i=0,$j=50; $i<100; $i++) {
while($j--) {
loop:
}
}
echo "$i = $i";
?>
上の例の出力は以下となります。
Fatal error: 'goto' into loop or switch statement is disallowed in script on line 2
注意:
goto 演算子は PHP 5.3 以降で使用可能です。
add a note
User Contributed Notes 14 notes
chrisstocktonaz at gmail dot com ¶
9 years ago
Ray dot Paseur at Gmail dot com ¶
7 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';
?>
D. Kellner ¶
3 years ago
However hated, goto is useful. When we say "useful" we don't mean "it should be used all the time" but that there are certain situations when it comes in handy.
There are times when you need a logical structure like this:
<?php
// ...
do {
$answer = checkFirstSource();
if(seemsGood($answer)) break;
$answer = readFromAnotherSource();
if(seemsGood($answer)) break;
// ...
}while(0);
$answer = applyFinalTouches($answer);
return $answer;
?>
In this case, you certainly implemented a goto with a "fake loop pattern". It could be a lot more readable with a goto; unless, of course, you hate it. But the logic is clear: try everything you can to get $answer, and whenever it seems good (e.g. not empty), jump happily to the point where you format it and give it back to the caller. It's a proper implementation of a simple fallback mechanism.
Basically, the fight against goto is just a side effect of a misleading article many decades ago. Those monsters are gone now. Feel free to use it when you know what you're doing.
R. Borchmann ¶
2 years ago
If you feel the urge to leave a nested loop with goto, better think again. Probably you've got a piece of your code that should be refactored into a function.
Instead of
<?php
for ($i=0; $i<10; $i++) {
for ($j=$i, $j<11; $j++) {
if ( $data[$i] === $data[$j] )
goto foundit;
}
}
echo "Sorry, no match";
goto nextAction;
foundit:
echo "Duplicate at $i and $j)";
nextAction:
?>
you better write
<?php
list($success, $i, $j) = searchForDuplicate( $data );
if ($success)
echo "Found it at ($i, $j)";
else
echo "Sorry, no match";
function searchForDuplicate( &$data )
{
for ($i=0; $i<10; $i++) {
for ($j=$i, $j<11; $j++) {
if ( $data[$i] === $data[$j] )
return [ true, $i, $j ];
}
}
return [false];
}
?>
or return [$i, $j] and [-1, -1] if you don't like an extra $success variable. Refactoring into a function is cleaner and gives you an auto-documentation about what the loop is doing.
sixoclockish at gmail dot com ¶
6 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:
?>
f at francislacroix dot info ¶
7 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.
at YearOfCodes (retrobytespr at mail dot com) ¶
1 year ago
Here is an example of re-using labels in separate methods - in this example, the end: label is used in each, with the goto condition behaving like an if/else condition:
class DateController
{
public $day, $month, $year;
public function __construct(){
$this->day = $this->setDays();
$this->month = $this->setMonths();
$this->year = $this->setYears(1901, (int)date('Y'), 'asc');
}
/**
* @param int
* @return array
*/
protected function setDays(int $default = 0){
$days = array();
for($i = 1; $i <= 31; $i++){
$day = "{$i}";
if($i<10){
$day = "0{$i}";
}
$days[$day] = $day;
}
if($default == 0){
goto end;
}
$days['default'] = $default;
end:
return $days;
}
/**
* @param string, string, string
* @return array
*/
protected function setMonths(string $type = "full", string $keyType = "numeric", string $default = ''){
$keys = array(
'numeric' => array(
"01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12"
),
'full' => array(
"January", "February", "March", "April", "May", "June", "July",
"August", "September", "October", "November", "December"
),
'short' => array(
"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
)
);
$months = array();
$index = 0;
foreach($keys[$keyType] as $primaryKey){
$months[$primaryKey] = $keys[$type][$index];
$index++;
}
if($default = ''){
goto end;
}
$months['default'] = $default;
end:
return $months;
}
/**
* @param int, int, string
* @return array
*/
protected function setYears(int $start = 1977, int $end = 2017, $order = "asc"){
$years = array();
if($order == "asc"){
for($i = $start; $i <= $end; $i++){
$years["{$i}"] = $i;
}
goto end;
}
for($i = $end; $i >= $start; $i--){
$years["{$i}"] = $i;
}
end:
return $years;
}
}
David Gimeno i Ayuso info at sima dot cat ¶
10 days ago
Goto isn't too advisable but sometimes it's a clearer solution than an if clause with a large number of instructions inside.
if ($error):
goto ExitFunction;
endif;
... a good bunch of lines ...
ExitFunction:
Anyway, what I would like to comment is maybe a gosub or perform operator will be useful too.
Many times I needed to create a separate function and pass a lot of variables to it just because there is a set of instructions I need to repeat in some parts of a process or function.
annoymous ¶
4 months ago
goto will be easy to use but also will be very easy to spoil your function so use it carefully.
romeu at gamelas dot pt ¶
4 months ago
This function despite it's bad name is pretty useful and the most CPU effective in to control a flow of multiple cascading situations.
Let's say you have some form set, but before it you need to perform a lot of checks on which form to show based upon user permissions or settings:
<?php
$user_info = ...; //something you get before from session, cookies, database...
if($user_info != "already_set"){
//Some setting need isn't yet done
loadForm("form1");
}else{
//OK, the set was done, so let's continue
if($user_info != "some_other_thing"){
//Another thing missing...
loadForm("form2");
}else{
//OK, the second part is done, let's do the third...
if($user_info != "some_yet_another_thing"){
//And yet another thing to setup...
loadForm("form3");
}else{
/* Guess you can see the picture now, it will be if(){ else if(){ else if(){ else....}}}}}}}}
}
}
}
?>
Goto can handle this situation like:
<?php
if($user_info != "already_set") {
loadForm("form1");
goto move_on;
}
if($user_info != "some_other_thing") {
loadForm("form2");
goto move_on;
}
if($user_info != "some_yet_another_thing") {
loadForm("form3");
goto move_on;
}
move_on:
?>
Preventing all other CMP instructions at the cascade with a simple JMP, "Assemblying speaking"
kle at lekhoi dot com ¶
2 years ago
Goto can also go into an infinite loop as the example below.
<?php
goto start;
start: echo 'start';
working: {
echo 'working';
...
goto start;
echo 'never executed';
}
?>
Output
startworkingstartworking ...
Mark ¶
1 year ago
Here are two examples of how GOTO can simplify code and actually make it more readable and easier to understand.
1. GOTO can be used to exit an IF block:
<?php
if(something) {
if(nothing) goto endif;
// blah blah
// blah blah
endif:
// Nothing here, but maybe some cleanup
}
?>
2. GOTO can be used to jump ahead to a section of code. This can be useful for trouble shooting or testing a script in small stages.
<?php
goto block3;
block1:
// blah blah
block2:
// blah blah
block3:
// blah blah
?>
Note that in both cases, I have gone forward, not backward. This makes it more manageable.
In the case of the IF block, many structures, such as a loop, a switch or a function, have an early exit, such as break or return. IF doesn’t, so this is a workable solution
ivan dot tc at gmail dot com ¶
3 years ago
This works good:
<?php
goto start;
five:
echo $i;
goto end;
start:
echo 'I have ';
for ($i=0; $i < 10; $i++) {
if ($i == 5) {
goto five;
}
}
end:
echo ' apples';
?>
Output: I have 5 apples.
This don't work:
<?php
goto start;
five:
echo $i;
goto end;
start:
echo 'I have ';
$count();
end:
echo ' apples';
$count = function () {
for ($i=0; $i < 10; $i++) {
if ($i == 5) {
goto five; // line 18
}
}
}
?>
PHP Fatal error: 'goto' to undefined label 'five' on line 18
ivan dot sammartino at gmail dot com ¶
3 years ago
I found it useful for switch statements:
<?php
$action = $_GET['action'];
switch ($action){
case('a'):
mylabel: {
doStuff();
break;
}
case('b'):
if (true){
doAnotherStuff();
} else {
goto mylabel;
}
break;
}
?>
