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goto

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

What's the worse thing that could happen if you use goto?

此漫画鸣谢 » xkcd

goto 操作符可以用来跳转到程序中的另一位置。该目标位置可以用 区分大小写 的目标名称加上冒号来标记,而跳转指令是 goto 之后接上目标位置的标记。PHP 中的 goto 有一定限制,目标位置只能位于同一个文件和作用域,也就是说无法跳出一个函数或类方法,也无法跳入到另一个函数。也无法跳入到任何循环或者 switch 结构中。可以跳出循环或者 switch,通常的用法是用 goto 代替多层的 break

示例 #1 goto 示例

<?php

goto a;
echo
'Foo';

a:
echo
'Bar';

?>

以上示例会输出:

Bar

示例 #2 goto 跳出循环示例

<?php

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

?>

以上示例会输出:

j hit 17

示例 #3 以下写法无效

<?php

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

?>

以上示例会输出:

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

add a note

User Contributed Notes 4 notes

up
51
Lollo
3 years ago
You should mention the label can't be a variable
up
26
devbyjesus at example dot com
2 years ago
the problem of goto is that it is a good feature but in a large codebase it reduces the readability of the code . that's all . i try to not use it to think about the person who is going to read after me .
up
3
BPI
1 year ago
You can jump inside the same switch. This can be usefull to jump to default
<?php
$x
=3;
switch(
$x){
case
0:
case
3:
print(
$x);
if(
$x)
goto
def;
case
5:
$x=6;
default:
def:
print(
$x);
}
?>
up
0
Anonymous
10 months ago
Example to exit loops:

for ($i = 0; $i < 10; $i++) {
for ($j = 0; $j < 10; $j++) {
if ($condition) {
goto exit;
}
}
}
exit:
echo "Out of the loop.";
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