torben Wed Jun 18 14:44:18 2003 EDT
Modified files:
/phpdoc/en/language types.xml
Log:
Clarify that you do not always quote array keys (i.e. when you're using
a variable or constant as a key).
Index: phpdoc/en/language/types.xml
diff -u phpdoc/en/language/types.xml:1.117 phpdoc/en/language/types.xml:1.118
--- phpdoc/en/language/types.xml:1.117 Wed Jun 18 14:19:07 2003
+++ phpdoc/en/language/types.xml Wed Jun 18 14:44:18 2003
@@ -1,5 +1,5 @@
<?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.117 $ -->
+<!-- $Revision: 1.118 $ -->
<chapter id="language.types">
<title>Types</title>
@@ -1513,9 +1513,10 @@
<sect3 id="language.types.array.foo-bar">
<title>Why is <literal>$foo[bar]</literal> wrong?</title>
<para>
- You should always use quotes around an associative array index.
- For example, use $foo['bar'] and not $foo[bar]. But why is $foo[bar]
- wrong? You might have seen the following syntax in old scripts:
+ You should always use quotes around a string literal
+ array index. For example, use $foo['bar'] and not
+ $foo[bar]. But why is $foo[bar] wrong? You might have seen the
+ following syntax in old scripts:
<informalexample>
<programlisting role="php">
<![CDATA[
@@ -1527,13 +1528,70 @@
]]>
</programlisting>
</informalexample>
- This is wrong, but it works. Then, why is it wrong? The reason is that
- this code has an undefined constant (bar) rather than a string ('bar' -
- notice the quotes), and PHP may in future define constants which,
- unfortunately for your code, have the same name. It works, because the
- undefined constant gets converted to a string of the same name
- automatically for backward compatibility reasons.
+ This is wrong, but it works. Then, why is it wrong? The reason
+ is that this code has an undefined constant (bar) rather than a
+ string ('bar' - notice the quotes), and PHP may in future define
+ constants which, unfortunately for your code, have the same
+ name. It works because PHP automatically converts a
+ <emphasis>bare string</emphasis> (an unquoted string which does
+ not correspond to any known symbol, such as constants) into a
+ string which contains the bare string. For instance, if there is
+ no defined constant named <constant>bar</constant>, then PHP
+ will substitute in the string <literal>'bar'</literal> and use
+ that.
</para>
+ <note>
+ <simpara>
+ This does not mean to <emphasis>always</emphasis> quote the
+ key. You do not want to quote keys which are <link
+ linkend="language.constants">constants</link> or <link
+ linkend="language.variables">variables</link>, as this will
+ prevent PHP from interpreting them.
+ </simpara>
+ <informalexample>
+ <programlisting role="php">
+<![CDATA[
+<?php
+error_reporting(E_ALL);
+ini_set('display_errors', true);
+ini_set('html_errors', false);
+// Simple array:
+$array = array(1, 2);
+$count = count($array);
+for ($i = 0; $i < $count; $i++) {
+ echo "\nChecking $i: \n";
+ echo "Bad: " . $array['$i'] . "\n";
+ echo "Good: " . $array[$i] . "\n";
+ echo "Bad: {$array['$i']}\n";
+ echo "Good: {$array[$i]}\n";
+}
+?>
+]]>
+ </programlisting>
+ </informalexample>
+ <para>
+ The output from the above is:
+ <screen>
+<![CDATA[
+Checking 0:
+Notice: Undefined index: $i in /path/to/script.html on line 9
+Bad:
+Good: 1
+Notice: Undefined index: $i in /path/to/script.html on line 11
+Bad:
+Good: 1
+
+Checking 1:
+Notice: Undefined index: $i in /path/to/script.html on line 9
+Bad:
+Good: 2
+Notice: Undefined index: $i in /path/to/script.html on line 11
+Bad:
+Good: 2
+]]>
+ </screen>
+ </para>
+ </note>
<para>
More examples to demonstrate this fact:
<informalexample>
@@ -1557,7 +1615,7 @@
// Let's define a constant to demonstrate what's going on. We
// will assign value 'veggie' to a constant named fruit.
-define('fruit','veggie');
+define('fruit', 'veggie');
// Notice the difference now
print $arr['fruit']; // apple
@@ -1593,10 +1651,11 @@
error_reporting</link> is turned down to not show them.
</para>
<para>
- As stated in the <link linkend="language.types.array.syntax"
- >syntax</link> section, there must be an expression between the
- square brackets ('<literal>[</literal>' and '<literal>]</literal>').
- That means that you can write things like this:
+ As stated in the <link
+ linkend="language.types.array.syntax">syntax</link> section,
+ there must be an expression between the square brackets
+ ('<literal>[</literal>' and '<literal>]</literal>'). That means
+ that you can write things like this:
<informalexample>
<programlisting role="php">
<