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><H1
><A
NAME="function.create-function"
></A
>create_function</H1
><DIV
CLASS="refnamediv"
><A
NAME="AEN62701"
></A
><P
>    (PHP 4 &#62;= 4.0.1, PHP 5)</P
>create_function&nbsp;--&nbsp;Create an anonymous (lambda-style) function</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN62704"
></A
><H2
>说明</H2
>string <B
CLASS="methodname"
>create_function</B
> ( string args, string code )<BR
></BR
><P
>&#13;   Creates an anonymous function from the parameters passed, and
   returns a unique name for it.
  </P
></DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN62716"
></A
><H2
>参数</H2
><P
>&#13;   Usually these parameters will be passed as single quote delimited strings.
   The reason for using single quoted strings, is to protect the variable
   names from parsing, otherwise, if you use double quotes there will be a
   need to escape the variable names, e.g. <TT
CLASS="literal"
>\$avar</TT
>.
   <P
></P
><DIV
CLASS="variablelist"
><DL
><DT
><CODE
CLASS="parameter"
>args</CODE
></DT
><DD
><P
>&#13;       The function arguments.
      </P
></DD
><DT
><CODE
CLASS="parameter"
>code</CODE
></DT
><DD
><P
>&#13;       The function code.
      </P
></DD
></DL
></DIV
>
  </P
></DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN62731"
></A
><H2
>返回值</H2
><P
>&#13;   Returns a unique function name as a string, or <TT
CLASS="constant"
><B
>FALSE</B
></TT
> on error.
  </P
></DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN62735"
></A
><H2
>范例</H2
><P
>&#13;   <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN62738"
></A
><P
><B
>例 1. 
     Creating an anonymous function with <B
CLASS="function"
>create_function()</B
>
    </B
></P
><P
>&#13;     You can use this function, to (for example) create a function from
     information gathered at run time:
    </P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br />$newfunc </font><font color="#007700">= </font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$a,$b'</font><font color="#007700">, </font><font color="#DD0000">'return "ln($a) + ln($b) = " . log($a * $b);'</font><font color="#007700">);<br />echo </font><font color="#DD0000">"New anonymous function: $newfunc</font><font color="#007700">\n</font><font color="#DD0000">"</font><font color="#007700">;<br />echo </font><font color="#0000BB">$newfunc</font><font color="#007700">(</font><font color="#0000BB">2</font><font color="#007700">, </font><font color="#0000BB">M_E</font><font color="#007700">) . </font><font color="#DD0000">"\n"</font><font color="#007700">;<br /></font><font color="#FF8000">// outputs<br />// New anonymous function: lambda_1<br />// ln(2) + ln(2.718281828459) = 1.6931471805599<br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
  </P
><P
>&#13;   Or, perhaps to have general handler function that can apply a set
   of operations to a list of parameters:
  </P
><P
>&#13;   <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN62745"
></A
><P
><B
>例 2. 
     Making a general processing function with
     <B
CLASS="function"
>create_function()</B
>
    </B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br /></font><font color="#007700">function </font><font color="#0000BB">process</font><font color="#007700">(</font><font color="#0000BB">$var1</font><font color="#007700">, </font><font color="#0000BB">$var2</font><font color="#007700">, </font><font color="#0000BB">$farr</font><font color="#007700">)<br />{<br />&nbsp;&nbsp;&nbsp;&nbsp;foreach (</font><font color="#0000BB">$farr </font><font color="#007700">as </font><font color="#0000BB">$f</font><font color="#007700">) {<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo </font><font color="#0000BB">$f</font><font color="#007700">(</font><font color="#0000BB">$var1</font><font color="#007700">, </font><font color="#0000BB">$var2</font><font color="#007700">) . </font><font color="#DD0000">"\n"</font><font color="#007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />}<br /><br /></font><font color="#FF8000">// create a bunch of math functions<br /></font><font color="#0000BB">$f1 </font><font color="#007700">= </font><font color="#DD0000">'if ($a &gt;=0) {return "b*a^2 = ".$b*sqrt($a);} else {return false;}'</font><font color="#007700">;<br /></font><font color="#0000BB">$f2 </font><font color="#007700">= </font><font color="#DD0000">"return \"min(b^2+a, a^2,b) = \".min(\$a*\$a+\$b,\$b*\$b+\$a);"</font><font color="#007700">;<br /></font><font color="#0000BB">$f3 </font><font color="#007700">= </font><font color="#DD0000">'if ($a &gt; 0 &amp;&amp; $b != 0) {return "ln(a)/b = ".log($a)/$b; } else { return false; }'</font><font color="#007700">;<br /></font><font color="#0000BB">$farr </font><font color="#007700">= array(<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$x,$y'</font><font color="#007700">, </font><font color="#DD0000">'return "some trig: ".(sin($x) + $x*cos($y));'</font><font color="#007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$x,$y'</font><font color="#007700">, </font><font color="#DD0000">'return "a hypotenuse: ".sqrt($x*$x + $y*$y);'</font><font color="#007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$a,$b'</font><font color="#007700">, </font><font color="#0000BB">$f1</font><font color="#007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$a,$b'</font><font color="#007700">, </font><font color="#0000BB">$f2</font><font color="#007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$a,$b'</font><font color="#007700">, </font><font color="#0000BB">$f3</font><font color="#007700">)<br />&nbsp;&nbsp;&nbsp;&nbsp;);<br /><br />echo </font><font color="#DD0000">"\nUsing the first array of anonymous functions\n"</font><font color="#007700">;<br />echo </font><font color="#DD0000">"parameters: 2.3445, M_PI\n"</font><font color="#007700">;<br /></font><font color="#0000BB">process</font><font color="#007700">(</font><font color="#0000BB">2.3445</font><font color="#007700">, </font><font color="#0000BB">M_PI</font><font color="#007700">, </font><font color="#0000BB">$farr</font><font color="#007700">);<br /><br /></font><font color="#FF8000">// now make a bunch of string processing functions<br /></font><font color="#0000BB">$garr </font><font color="#007700">= array(<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$b,$a'</font><font color="#007700">, </font><font color="#DD0000">'if (strncmp($a, $b, 3) == 0) return "** \"$a\" '</font><font color="#007700">.<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#DD0000">'and \"$b\"\n** Look the same to me! (looking at the first 3 chars)";'</font><font color="#007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$a,$b'</font><font color="#007700">, </font><font color="#DD0000">'; return "CRCs: " . crc32($a) . " , ".crc32(b);'</font><font color="#007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$a,$b'</font><font color="#007700">, </font><font color="#DD0000">'; return "similar(a,b) = " . similar_text($a, $b, &amp;$p) . "($p%)";'</font><font color="#007700">)<br />&nbsp;&nbsp;&nbsp;&nbsp;);<br />echo </font><font color="#DD0000">"\nUsing the second array of anonymous functions\n"</font><font color="#007700">;<br /></font><font color="#0000BB">process</font><font color="#007700">(</font><font color="#DD0000">"Twas brilling and the slithy toves"</font><font color="#007700">, </font><font color="#DD0000">"Twas the night"</font><font color="#007700">, </font><font color="#0000BB">$garr</font><font color="#007700">);<br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
><P
>上例将输出：</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>Using the first array of anonymous functions
parameters: 2.3445, M_PI
some trig: -1.6291725057799
a hypotenuse: 3.9199852871011
b*a^2 = 4.8103313314525
min(b^2+a, a^2,b) = 8.6382729035898
ln(a/b) = 0.27122299212594

Using the second array of anonymous functions
** "Twas the night" and "Twas brilling and the slithy toves"
** Look the same to me! (looking at the first 3 chars)
CRCs: -725381282 , 1908338681
similar(a,b) = 11(45.833333333333%)</PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
  </P
><P
>&#13;   But perhaps the most common use for of lambda-style (anonymous) functions
   is to create callback functions, for example when using
   <A
HREF="function.array-walk.html"
><B
CLASS="function"
>array_walk()</B
></A
> or <A
HREF="function.usort.html"
><B
CLASS="function"
>usort()</B
></A
>
  </P
><P
>&#13;   <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN62755"
></A
><P
><B
>例 3. Using anonymous functions as callback functions</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br />$av </font><font color="#007700">= array(</font><font color="#DD0000">"the "</font><font color="#007700">, </font><font color="#DD0000">"a "</font><font color="#007700">, </font><font color="#DD0000">"that "</font><font color="#007700">, </font><font color="#DD0000">"this "</font><font color="#007700">);<br /></font><font color="#0000BB">array_walk</font><font color="#007700">(</font><font color="#0000BB">$av</font><font color="#007700">, </font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'&amp;$v,$k'</font><font color="#007700">, </font><font color="#DD0000">'$v = $v . "mango";'</font><font color="#007700">));<br /></font><font color="#0000BB">print_r</font><font color="#007700">(</font><font color="#0000BB">$av</font><font color="#007700">);<br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
><P
>上例将输出：</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>Array
(
  [0] =&#62; the mango
  [1] =&#62; a mango
  [2] =&#62; that mango
  [3] =&#62; this mango
)</PRE
></TD
></TR
></TABLE
><P
>&#13;     an array of strings ordered from shorter to longer
    </P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br /><br />$sv </font><font color="#007700">= array(</font><font color="#DD0000">"small"</font><font color="#007700">, </font><font color="#DD0000">"larger"</font><font color="#007700">, </font><font color="#DD0000">"a big string"</font><font color="#007700">, </font><font color="#DD0000">"it is a string thing"</font><font color="#007700">);<br /></font><font color="#0000BB">print_r</font><font color="#007700">(</font><font color="#0000BB">$sv</font><font color="#007700">);<br /><br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
><P
>上例将输出：</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>Array
(
  [0] =&#62; small
  [1] =&#62; larger
  [2] =&#62; a big string
  [3] =&#62; it is a string thing
)</PRE
></TD
></TR
></TABLE
><P
>&#13;     sort it from longer to shorter
    </P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB">&lt;?php<br /><br />usort</font><font color="#007700">(</font><font color="#0000BB">$sv</font><font color="#007700">, </font><font color="#0000BB">create_function</font><font color="#007700">(</font><font color="#DD0000">'$a,$b'</font><font color="#007700">,</font><font color="#DD0000">'return strlen($b) - strlen($a);'</font><font color="#007700">));<br /></font><font color="#0000BB">print_r</font><font color="#007700">(</font><font color="#0000BB">$sv</font><font color="#007700">);<br /><br /></font><font color="#0000BB">?&gt;</font>
</font>
</code></TD
></TR
></TABLE
><P
>上例将输出：</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>Array
(
  [0] =&#62; it is a string thing
  [1] =&#62; a big string
  [2] =&#62; larger
  [3] =&#62; small
)</PRE
></TD
></TR
></TABLE
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