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Moving section on "How to read a function definition" here from tutorial.xml
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@97337 c90b9560-bf6c-de11-be94-00142212c4b1
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Philip Olson
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1 changed files with 128 additions and 1 deletions
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<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.16 $ -->
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<!-- $Revision: 1.17 $ -->
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<!--
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TODO: add manual conventions section (eg. how to read
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@ -111,6 +111,133 @@
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</para>
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</note>
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</sect1>
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<sect1 id="about.prototypes">
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<title>How to read a function definition (prototype)</title>
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<para>
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Each function is documented for quick reference, knowing how
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to read and understand the manual will make using PHP
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much easier. Rather than relying on examples or cut/paste, you want
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to know how to read function definitions (prototypes). Let's begin:
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</para>
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<note>
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<title>
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Prerequisite: Basic understanding of <link linkend="language.types">types</link>
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</title>
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<para>
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Although PHP is a loosly typed language, it's important to have
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a basic understanding of <link linkend="language.types">types</link> as
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they have important meaning.
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</para>
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</note>
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<para>
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Function definitions tell us what
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type of value is <link linkend="functions.returning-values">returned</link>,
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let's use the definition for <function>strlen</function> as our first example:
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</para>
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<para>
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<screen role="html">
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strlen
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(PHP 3, PHP 4 >= 4.0.0)
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strlen -- Get string length
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Description
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int strlen ( string str )
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Returns the length of string.
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</screen>
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</para>
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<para>
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<table>
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<title>Explanation of a function definition</title>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>Part</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>
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strlen
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</entry>
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<entry>
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The function name.
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</entry>
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</row>
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<row>
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<entry>
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(PHP 3, PHP 4 >= 4.0.0)
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</entry>
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<entry>
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strlen() has been around in both all of PHP 3 and PHP 4
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</entry>
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</row>
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<row>
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<entry>
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int
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</entry>
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<entry>
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Type of value this function returns, which is an
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<link linkend="language.types.integer">integer</link>
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(i.e. The length of a string is measured in numbers).
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</entry>
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</row>
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<row>
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<entry>
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( string str )
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</entry>
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<entry>
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The first (and in this case the only) parameter/argument for the
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function strlen() is named <parameter>str</parameter>, and it's a
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<link linkend="language.types.string">string</link>.
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</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</para>
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<para>
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We could rewrite the above function definition in a generic way:
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</para>
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<para>
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<screen role="html">
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returned type function name ( parameter type parameter name )
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</screen>
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</para>
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<para>
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Many functions take on multiple parameters, such as <function>in_array</function>.
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It's prototype is as follows:
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</para>
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<para>
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<screen role="html">
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bool in_array ( mixed needle, array haystack [, bool strict])
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</screen>
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</para>
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<para>
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What does this mean? in_array() returns a
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<link linkend="language.types.boolean">boolean</link> value, &true; on
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success (the <parameter>needle</parameter> was found in the
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<parameter>haystack</parameter>) or &false; on failure (the
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<parameter>needle</parameter> was not found in the
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<parameter>haystack</parameter>). The first parameter is named
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<parameter>needle</parameter> and it can be many different
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<link linkend="language.types">types</link>, so we call it
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"<emphasis>mixed</emphasis>". This mixed <parameter>needle</parameter>
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(what we're looking for) can either be a scalar value (string, integer,
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or <link linkend="language.types.float">float</link>), or an
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<link linkend="language.types.array">array</link>.
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<parameter>haystack</parameter> (the array we're searching in) is the
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second parameter. The third <emphasis>optional</emphasis> parameter is
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named <parameter>strict</parameter>. All optional parameters are seen
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in <emphasis>[</emphasis> brackets <emphasis>]</emphasis>. The manual
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states that the <parameter>strict</parameter> parameter defaults to
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boolean &false;. See the manual page on each function for details on
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how they work.
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</para>
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</sect1>
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<sect1 id="about.more">
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<title>How to find more information about PHP</title>
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