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>How to read a function definition (prototype)</TITLE
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><H1
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><A
NAME="about.prototypes"
></A
>How to read a function definition (prototype)</H1
><P
>&#13;    Each function is documented for quick reference, knowing how 
    to read and understand the manual will make using PHP 
    much easier.  Rather than relying on examples or cut/paste, you want 
    to know how to read function definitions (prototypes).  Let's begin:
   </P
><DIV
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CLASS="note"
><P
><B
>Prerequisite: Basic understanding of <A
HREF="language.types.html"
>types</A
>: </B
>
     Although PHP is a loosly typed language, it's important to have 
     a basic understanding of <A
HREF="language.types.html"
>types</A
> as 
     they have important meaning.
    </P
></BLOCKQUOTE
></DIV
><P
>&#13;    Function definitions tell us what 
    type of value is <A
HREF="functions.returning-values.html"
>returned</A
>, 
    let's use the definition for <A
HREF="function.strlen.html"
><B
CLASS="function"
>strlen()</B
></A
> as our first example:
   </P
><P
>&#13;    <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="html"
>strlen

(PHP 3, PHP 4 &#62;= 4.0.0)
strlen -- Get string length

Description
int strlen ( string str )

Returns the length of string.</PRE
></TD
></TR
></TABLE
>
   </P
><P
>&#13;    <DIV
CLASS="table"
><A
NAME="AEN111260"
></A
><P
><B
>Table K-1. Explanation of a function definition</B
></P
><TABLE
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><THEAD
><TR
><TH
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>Part</TH
><TH
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VALIGN="MIDDLE"
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;          strlen
         </TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;          The function name.
         </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;          (PHP 3, PHP 4 &#62;= 4.0.0)
         </TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;          strlen() has been around in both all of PHP 3 and PHP 4
         </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;          int
         </TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;          Type of value this function returns, which is an 
          <A
HREF="language.types.integer.html"
>integer</A
>
          (i.e. The length of a string is measured in numbers).
         </TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;          ( string str )
         </TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>&#13;          The first (and in this case the only) parameter/argument for the 
          function strlen() is named <TT
CLASS="parameter"
><I
>str</I
></TT
>, and it's a 
          <A
HREF="language.types.string.html"
>string</A
>.
         </TD
></TR
></TBODY
></TABLE
></DIV
>
    </P
><P
>&#13;     We could rewrite the above function definition in a generic way:
    </P
><P
>&#13;     <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="html"
>returned type    function name    ( parameter type   parameter name )</PRE
></TD
></TR
></TABLE
>
    </P
><P
>&#13;     Many functions take on multiple parameters, such as <A
HREF="function.in-array.html"
><B
CLASS="function"
>in_array()</B
></A
>.
     It's prototype is as follows:
    </P
><P
>&#13;     <TABLE
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><TR
><TD
><PRE
CLASS="html"
>bool in_array ( mixed needle, array haystack [, bool strict])</PRE
></TD
></TR
></TABLE
>
    </P
><P
>&#13;     What does this mean?  in_array() returns a 
     <A
HREF="language.types.boolean.html"
>boolean</A
> value, <TT
CLASS="constant"
><B
>TRUE</B
></TT
> on 
     success (the <TT
CLASS="parameter"
><I
>needle</I
></TT
> was found in the 
     <TT
CLASS="parameter"
><I
>haystack</I
></TT
>) or <TT
CLASS="constant"
><B
>FALSE</B
></TT
> on failure (the 
     <TT
CLASS="parameter"
><I
>needle</I
></TT
> was not found in the 
     <TT
CLASS="parameter"
><I
>haystack</I
></TT
>).  The first parameter is named 
     <TT
CLASS="parameter"
><I
>needle</I
></TT
> and it can be many different 
     <A
HREF="language.types.html"
>types</A
>, so we call it 
     "<SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>mixed</I
></SPAN
>".  This mixed <TT
CLASS="parameter"
><I
>needle</I
></TT
> 
     (what we're looking for) can either be a scalar value (string, integer, 
     or <A
HREF="language.types.float.html"
>float</A
>), or an
     <A
HREF="language.types.array.html"
>array</A
>.  
     <TT
CLASS="parameter"
><I
>haystack</I
></TT
> (the array we're searching in) is the 
     second parameter.  The third <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>optional</I
></SPAN
> parameter is 
     named <TT
CLASS="parameter"
><I
>strict</I
></TT
>.  All optional parameters are seen 
     in <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>[</I
></SPAN
> brackets <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>]</I
></SPAN
>.  The manual 
     states that the <TT
CLASS="parameter"
><I
>strict</I
></TT
> parameter defaults to 
     boolean <TT
CLASS="constant"
><B
>FALSE</B
></TT
>.  See the manual page on each function for details on 
     how they work.
    </P
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