1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
|
<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 293274 $ -->
<sect1 xml:id="control-structures.goto" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<title><literal>goto</literal></title>
<para>
The <literal>goto</literal> operator can be used to jump to another
section in the program. The target point is specified by a label
followed by a colon, and the instruction is given as
<literal>goto</literal> followed by the desired target label. This
is not a full unrestricted <literal>goto</literal>. The target
label must be within the same file and context, meaning that you cannot jump
out of a function or method, nor can you jump into one. You also
cannot jump into any sort of loop or switch structure. You may jump
out of these, and a common use is to use a <literal>goto</literal>
in place of a multi-level <literal>break</literal>.
</para>
<para>
<example>
<title><literal>goto</literal> example</title>
<programlisting role="php">
<![CDATA[
<?php
goto a;
echo 'Foo';
a:
echo 'Bar';
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
Bar
]]>
</screen>
</example>
</para>
<para>
<example>
<title><literal>goto</literal> loop example</title>
<programlisting role="php">
<![CDATA[
<?php
for($i=0,$j=50; $i<100; $i++) {
while($j--) {
if($j==17) goto end;
}
}
echo "i = $i";
end:
echo 'j hit 17';
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
j hit 17
]]>
</screen>
</example>
</para>
<para>
<example>
<title>This will not work</title>
<programlisting role="php">
<![CDATA[
<?php
goto loop;
for($i=0,$j=50; $i<100; $i++) {
while($j--) {
loop:
}
}
echo "$i = $i";
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
Fatal error: 'goto' into loop or switch statement is disallowed in
script on line 2
]]>
</screen>
</example>
</para>
<note>
<para>
The <literal>goto</literal> operator is available as of PHP 5.3.
</para>
</note>
<para>
<mediaobject>
<alt>What's the worse thing that could happen if you use goto?</alt>
<imageobject>
<imagedata fileref="en/language/figures/xkcd-goto.png" format="PNG"/>
</imageobject>
</mediaobject>
Image courtesy of <link xlink:href="&url.xkcd;292">xkcd</link>
</para>
</sect1>
<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
indent-tabs-mode:nil
sgml-parent-document:nil
sgml-default-dtd-file:"~/.phpdoc/manual.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim600: syn=xml fen fdm=syntax fdl=2 si
vim: et tw=78 syn=sgml
vi: ts=1 sw=1
-->
|
