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
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
|
<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.array-walk" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>array_walk</refname>
<refpurpose>Apply a user supplied function to every member of an array</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>true</type><methodname>array_walk</methodname>
<methodparam><type class="union"><type>array</type><type>object</type></type><parameter role="reference">array</parameter></methodparam>
<methodparam><type>callable</type><parameter>callback</parameter></methodparam>
<methodparam choice="opt"><type>mixed</type><parameter>arg</parameter><initializer>&null;</initializer></methodparam>
</methodsynopsis>
<simpara>
Applies the user-defined <parameter>callback</parameter> function to each
element of the <parameter>array</parameter> array.
</simpara>
<para>
<function>array_walk</function> is not affected by the internal array
pointer of <parameter>array</parameter>. <function>array_walk</function>
will walk through the entire array regardless of pointer position.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>array</parameter></term>
<listitem>
<para>
The input array.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>callback</parameter></term>
<listitem>
<para>
Typically, <parameter>callback</parameter> takes on two parameters.
The <parameter>array</parameter> parameter's value being the first, and
the key/index second.
</para>
<note>
<para>
If <parameter>callback</parameter> needs to be working with the
actual values of the array, specify the first parameter of
<parameter>callback</parameter> as a
<link linkend="language.references">reference</link>. Then,
any changes made to those elements will be made in the
original array itself.
</para>
</note>
<note>
<para>
Many internal functions (for example <function>strtolower</function>)
will throw a warning if more than the expected number of argument
are passed in and are not usable directly as a
<parameter>callback</parameter>.
</para>
</note>
<para>
Only the values of the <parameter>array</parameter> may potentially be
changed; its structure cannot be altered, i.e., the programmer cannot
add, unset or reorder elements. If the callback does not respect this
requirement, the behavior of this function is undefined, and
unpredictable.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>arg</parameter></term>
<listitem>
<para>
If the optional <parameter>arg</parameter> parameter is supplied,
it will be passed as the third parameter to the
<parameter>callback</parameter>.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
&return.true.always;
</para>
</refsect1>
<refsect1 role="errors">
&reftitle.errors;
<para>
As of PHP 7.1.0, an <classname>ArgumentCountError</classname> will be thrown if the <parameter>callback</parameter> function
requires more than 2 parameters (the value and key of the array member),
or more than 3 parameters if the <parameter>arg</parameter> is also passed.
Previously, in this case
an error of level <link linkend="errorfunc.constants">E_WARNING</link> would be generated each time
<function>array_walk</function> calls <parameter>callback</parameter>.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
&return.type.true;
<row>
<entry>8.0.0</entry>
<entry>
If <parameter>callback</parameter> expects the second or third parameter to be passed
by reference, this function will now emit an <constant>E_WARNING</constant>.
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title><function>array_walk</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");
function test_alter(&$item1, $key, $prefix)
{
$item1 = "$prefix: $item1";
}
function test_print($item2, $key)
{
echo "$key. $item2\n";
}
echo "Before ...:\n";
array_walk($fruits, 'test_print');
array_walk($fruits, 'test_alter', 'fruit');
echo "... and after:\n";
array_walk($fruits, 'test_print');
?>
]]>
</programlisting>
&example.outputs;
<screen role="php">
<![CDATA[
Before ...:
d. lemon
a. orange
b. banana
c. apple
... and after:
d. fruit: lemon
a. fruit: orange
b. fruit: banana
c. fruit: apple
]]>
</screen>
</example>
</para>
<para>
<example>
<title><function>array_walk</function> example using anonymous function</title>
<programlisting role="php">
<![CDATA[
<?php
$elements = ['a', 'b', 'c'];
array_walk($elements, function ($value, $key) {
echo "{$key} => {$value}\n";
});
?>
]]>
</programlisting>
&example.outputs;
<screen role="php">
<![CDATA[
0 => a
1 => b
2 => c
]]>
</screen>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>array_walk_recursive</function></member>
<member><function>iterator_apply</function></member>
<member><function>list</function></member>
<member><function>each</function></member>
<member><function>call_user_func_array</function></member>
<member><function>array_map</function></member>
<member>&foreach;</member>
</simplelist>
</para>
</refsect1>
</refentry>
<!-- 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
-->
|
