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Source of: /manual/en/function.create-function.php

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<div id="function.create-function" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">create_function</h1>
  <p class="verinfo">(PHP 4 &gt;= 4.0.1, PHP 5)</p><p class="refpurpose"><span class="refname">create_function</span> &mdash; <span class="dc-title">Create an anonymous (lambda-style) function</span></p>

 </div>

 <a name="function.create-function.description"></a><div class="refsect1 description">
  <h3 class="title">Description</h3>
  <div class="methodsynopsis dc-description">
   <span class="type">string</span> <span class="methodname"><b>create_function</b></span>
    ( <span class="methodparam"><span class="type">string</span> <tt class="parameter">$args</tt></span>
   , <span class="methodparam"><span class="type">string</span> <tt class="parameter">$code</tt></span>
   )</div>

  <p class="para rdfs-comment">
   Creates an anonymous function from the parameters passed, and
   returns a unique name for it.
  </p>
 </div>

 <a name="function.create-function.parameters"></a><div class="refsect1 parameters">
  <h3 class="title">Parameters</h3>
  <p class="para">
   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. <i>\$avar</i>.
   </p><dl>

    <dt class="varlistentry">

     <span class="term"><i><tt class="parameter">args</tt></i>
</span>

     </dt><dd class="listitem">

      <p class="para">
       The function arguments.
      </p>
     </dd>

   
    <dt class="varlistentry">

     <span class="term"><i><tt class="parameter">code</tt></i>
</span>

     </dt><dd class="listitem">

      <p class="para">
       The function code.
      </p>
     </dd>

   
   </dl>
<p>
  </p>
 </div>


 <a name="function.create-function.returnvalues"></a><div class="refsect1 returnvalues">
  <h3 class="title">Return Values</h3>
  <p class="para">
   Returns a unique function name as a string, or <b><tt class="constant">FALSE</tt></b> on error.
  </p>
 </div>


 <a name="function.create-function.examples"></a><div class="refsect1 examples">
  <h3 class="title">Examples</h3>
  <p class="para">
   </p><div class="example">
    <p><b>Example #1
     Creating an anonymous function with <b>create_function()</b>
    </b></p>
    <div class="example-contents para"><p>
     You can use this function, to (for example) create a function from
     information gathered at run time:
    </p></div>
    <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$newfunc&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$a,$b'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'return&nbsp;"ln($a)&nbsp;+&nbsp;ln($b)&nbsp;=&nbsp;"&nbsp;.&nbsp;log($a&nbsp;*&nbsp;$b);'</span><span style="color: #007700">);<br />echo&nbsp;</span><span style="color: #DD0000">"New&nbsp;anonymous&nbsp;function:&nbsp;</span><span style="color: #0000BB">$newfunc</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;<br />echo&nbsp;</span><span style="color: #0000BB">$newfunc</span><span style="color: #007700">(</span><span style="color: #0000BB">2</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">M_E</span><span style="color: #007700">)&nbsp;.&nbsp;</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /></span><span style="color: #FF8000">//&nbsp;outputs<br />//&nbsp;New&nbsp;anonymous&nbsp;function:&nbsp;lambda_1<br />//&nbsp;ln(2)&nbsp;+&nbsp;ln(2.718281828459)&nbsp;=&nbsp;1.6931471805599<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div><p>
  </p>
  <p class="para">
   Or, perhaps to have general handler function that can apply a set
   of operations to a list of parameters:
  </p>
  <p class="para">
   </p><div class="example">
    <p><b>Example #2
     Making a general processing function with
     <b>create_function()</b>
    </b></p>
    <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">process</span><span style="color: #007700">(</span><span style="color: #0000BB">$var1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$var2</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$farr</span><span style="color: #007700">)<br />{<br />&nbsp;&nbsp;&nbsp;&nbsp;foreach&nbsp;(</span><span style="color: #0000BB">$farr&nbsp;</span><span style="color: #007700">as&nbsp;</span><span style="color: #0000BB">$f</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #0000BB">$f</span><span style="color: #007700">(</span><span style="color: #0000BB">$var1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$var2</span><span style="color: #007700">)&nbsp;.&nbsp;</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />}<br /><br /></span><span style="color: #FF8000">//&nbsp;create&nbsp;a&nbsp;bunch&nbsp;of&nbsp;math&nbsp;functions<br /></span><span style="color: #0000BB">$f1&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'if&nbsp;($a&nbsp;&gt;=0)&nbsp;{return&nbsp;"b*a^2&nbsp;=&nbsp;".$b*sqrt($a);}&nbsp;else&nbsp;{return&nbsp;false;}'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$f2&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">"return&nbsp;\"min(b^2+a,&nbsp;a^2,b)&nbsp;=&nbsp;\".min(\$a*\$a+\$b,\$b*\$b+\$a);"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$f3&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'if&nbsp;($a&nbsp;&gt;&nbsp;0&nbsp;&amp;&amp;&nbsp;$b&nbsp;!=&nbsp;0)&nbsp;{return&nbsp;"ln(a)/b&nbsp;=&nbsp;".log($a)/$b;&nbsp;}&nbsp;else&nbsp;{&nbsp;return&nbsp;false;&nbsp;}'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$farr&nbsp;</span><span style="color: #007700">=&nbsp;array(<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$x,$y'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'return&nbsp;"some&nbsp;trig:&nbsp;".(sin($x)&nbsp;+&nbsp;$x*cos($y));'</span><span style="color: #007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$x,$y'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'return&nbsp;"a&nbsp;hypotenuse:&nbsp;".sqrt($x*$x&nbsp;+&nbsp;$y*$y);'</span><span style="color: #007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$a,$b'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$f1</span><span style="color: #007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$a,$b'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$f2</span><span style="color: #007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$a,$b'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$f3</span><span style="color: #007700">)<br />&nbsp;&nbsp;&nbsp;&nbsp;);<br /><br />echo&nbsp;</span><span style="color: #DD0000">"\nUsing&nbsp;the&nbsp;first&nbsp;array&nbsp;of&nbsp;anonymous&nbsp;functions\n"</span><span style="color: #007700">;<br />echo&nbsp;</span><span style="color: #DD0000">"parameters:&nbsp;2.3445,&nbsp;M_PI\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">process</span><span style="color: #007700">(</span><span style="color: #0000BB">2.3445</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">M_PI</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$farr</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;now&nbsp;make&nbsp;a&nbsp;bunch&nbsp;of&nbsp;string&nbsp;processing&nbsp;functions<br /></span><span style="color: #0000BB">$garr&nbsp;</span><span style="color: #007700">=&nbsp;array(<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$b,$a'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'if&nbsp;(strncmp($a,&nbsp;$b,&nbsp;3)&nbsp;==&nbsp;0)&nbsp;return&nbsp;"**&nbsp;\"$a\"&nbsp;'</span><span style="color: #007700">.<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'and&nbsp;\"$b\"\n**&nbsp;Look&nbsp;the&nbsp;same&nbsp;to&nbsp;me!&nbsp;(looking&nbsp;at&nbsp;the&nbsp;first&nbsp;3&nbsp;chars)";'</span><span style="color: #007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$a,$b'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">';&nbsp;return&nbsp;"CRCs:&nbsp;"&nbsp;.&nbsp;crc32($a)&nbsp;.&nbsp;"&nbsp;,&nbsp;".crc32(b);'</span><span style="color: #007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$a,$b'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">';&nbsp;return&nbsp;"similar(a,b)&nbsp;=&nbsp;"&nbsp;.&nbsp;similar_text($a,&nbsp;$b,&nbsp;&amp;$p)&nbsp;.&nbsp;"($p%)";'</span><span style="color: #007700">)<br />&nbsp;&nbsp;&nbsp;&nbsp;);<br />echo&nbsp;</span><span style="color: #DD0000">"\nUsing&nbsp;the&nbsp;second&nbsp;array&nbsp;of&nbsp;anonymous&nbsp;functions\n"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">process</span><span style="color: #007700">(</span><span style="color: #DD0000">"Twas&nbsp;brilling&nbsp;and&nbsp;the&nbsp;slithy&nbsp;toves"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"Twas&nbsp;the&nbsp;night"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$garr</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents para"><p>The above example will output:</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
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
** &quot;Twas the night&quot; and &quot;Twas brilling and the slithy toves&quot;
** Look the same to me! (looking at the first 3 chars)
CRCs: -725381282 , 1908338681
similar(a,b) = 11(45.833333333333%)
</pre></div>
    </div>
   </div><p>
  </p>
  <p class="para">
   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.php" class="function">array_walk()</a> or <a href="function.usort.php" class="function">usort()</a>
  </p>
  <p class="para">
   </p><div class="example">
    <p><b>Example #3 Using anonymous functions as callback functions</b></p>
    <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$av&nbsp;</span><span style="color: #007700">=&nbsp;array(</span><span style="color: #DD0000">"the&nbsp;"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"a&nbsp;"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"that&nbsp;"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"this&nbsp;"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">array_walk</span><span style="color: #007700">(</span><span style="color: #0000BB">$av</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'&amp;$v,$k'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'$v&nbsp;=&nbsp;$v&nbsp;.&nbsp;"mango";'</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$av</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents para"><p>The above example will output:</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
Array
(
  [0] =&gt; the mango
  [1] =&gt; a mango
  [2] =&gt; that mango
  [3] =&gt; this mango
)
</pre></div>
    </div>
    <div class="example-contents para"><p>
     an array of strings ordered from shorter to longer
    </p></div>
    <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br />$sv&nbsp;</span><span style="color: #007700">=&nbsp;array(</span><span style="color: #DD0000">"small"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"larger"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"a&nbsp;big&nbsp;string"</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"it&nbsp;is&nbsp;a&nbsp;string&nbsp;thing"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$sv</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents para"><p>The above example will output:</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
Array
(
  [0] =&gt; small
  [1] =&gt; larger
  [2] =&gt; a big string
  [3] =&gt; it is a string thing
)
</pre></div>
    </div>
    <div class="example-contents para"><p>
     sort it from longer to shorter
    </p></div>
    <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br />usort</span><span style="color: #007700">(</span><span style="color: #0000BB">$sv</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">create_function</span><span style="color: #007700">(</span><span style="color: #DD0000">'$a,$b'</span><span style="color: #007700">,</span><span style="color: #DD0000">'return&nbsp;strlen($b)&nbsp;-&nbsp;strlen($a);'</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$sv</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents para"><p>The above example will output:</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
Array
(
  [0] =&gt; it is a string thing
  [1] =&gt; a big string
  [2] =&gt; larger
  [3] =&gt; small
)
</pre></div>
    </div>
   </div><p>
  </p>
 </div>


 <a name="function.create-function.seealso"></a><div class="refsect1 seealso">
  <h3 class="title">See Also</h3>
  <p class="para">
   </p><ul class="simplelist">
    <li class="member"><a href="functions.anonymous.php" class="link">Anonymous functions</a></li>
   </ul><p>
  </p>
 </div>


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