language.types.array.html

php的帮助文档,涉及到PHP的案例和基本语法,以及实际应用内容

<span style="color: #0000BB">&lt;?php<br />$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">E_ERROR</span><span style="color: #007700">]&nbsp;&nbsp;&nbsp;=&nbsp;</span><span style="color: #DD0000">"A&nbsp;fatal&nbsp;error&nbsp;has&nbsp;occured"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">E_WARNING</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #DD0000">"PHP&nbsp;issued&nbsp;a&nbsp;warning"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">E_NOTICE</span><span style="color: #007700">]&nbsp;&nbsp;=&nbsp;</span><span style="color: #DD0000">"This&nbsp;is&nbsp;just&nbsp;an&nbsp;informal&nbsp;notice"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div>
   
   <p class="para">
    Note that <i>E_ERROR</i> is also a valid identifier, just like
    <i>bar</i> in the first example. But the last example is in fact
    the same as writing:
   </p>
  
   <div class="informalexample">
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">1</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #DD0000">"A&nbsp;fatal&nbsp;error&nbsp;has&nbsp;occured"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">2</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #DD0000">"PHP&nbsp;issued&nbsp;a&nbsp;warning"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$error_descriptions</span><span style="color: #007700">[</span><span style="color: #0000BB">8</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #DD0000">"This&nbsp;is&nbsp;just&nbsp;an&nbsp;informal&nbsp;notice"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div>
   
   <p class="para">
    because <i>E_ERROR</i> equals <i>1</i>, etc.
   </p>

   <div id="language.types.array.foo-bar.why" class="sect4">
    <h5 class="title">So why is it bad then?</h5>

    <p class="para">
     At some point in the future, the PHP team might want to add another
     constant or keyword, or a constant in other code may interfere. For
     example, it is already wrong to use the words <i>empty</i> and
     <i>default</i> this way, since they are
     <a href="reserved.html" class="link">reserved keywords</a>.
    </p>

    <blockquote><p><b class="note">Note</b>: 
     <span class="simpara">
      To reiterate, inside a double-quoted <a href="language.types.string.html" class="type string">string</a>, it&#039;s valid to
      not surround array indexes with quotes so <i>&quot;$foo[bar]&quot;</i>
      is valid. See the above examples for details on why as well as the section
      on <a href="language.types.string.html#language.types.string.parsing" class="link">variable parsing in
      strings</a>.
     </span>
    </p></blockquote>

   </div>
  </div>
 </div>

 <div id="language.types.array.casting" class="sect2">
  <h3 class="title">Converting to array</h3>
  
  <p class="para">
   For any of the types: <a href="language.types.integer.html" class="type integer">integer</a>, <a href="language.types.float.html" class="type float">float</a>,
   <a href="language.types.string.html" class="type string">string</a>, <a href="language.types.boolean.html" class="type boolean">boolean</a> and <a href="language.types.resource.html" class="type resource">resource</a>,
   converting a value to an <a href="language.types.array.html" class="type array">array</a> results in an array with a single
   element with index zero and the value of the scalar which was converted. In
   other words, <i>(array)$scalarValue</i> is exactly the same as
   <i>array($scalarValue)</i>.
  </p>
  
  <p class="para">
   If an <a href="language.types.object.html" class="type object">object</a> is converted to an <a href="language.types.array.html" class="type array">array</a>, the result
   is an <a href="language.types.array.html" class="type array">array</a> whose elements are the <a href="language.types.object.html" class="type object">object</a>&#039;s
   properties. The keys are the member variable names, with a few notable
   exceptions: private variables have the class name prepended to the variable
   name; protected variables have a &#039;*&#039; prepended to the variable name. These
   prepended values have null bytes on either side. This can result in some
   unexpected behaviour:
  </p>

  <div class="informalexample">
   <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">A&nbsp;</span><span style="color: #007700">{<br />&nbsp;&nbsp;&nbsp;&nbsp;private&nbsp;</span><span style="color: #0000BB">$A</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;This&nbsp;will&nbsp;become&nbsp;'\0A\0A'<br /></span><span style="color: #007700">}<br /><br />class&nbsp;</span><span style="color: #0000BB">B&nbsp;</span><span style="color: #007700">extends&nbsp;</span><span style="color: #0000BB">A&nbsp;</span><span style="color: #007700">{<br />&nbsp;&nbsp;&nbsp;&nbsp;private&nbsp;</span><span style="color: #0000BB">$A</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;This&nbsp;will&nbsp;become&nbsp;'\0B\0A'<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">public&nbsp;</span><span style="color: #0000BB">$AA</span><span style="color: #007700">;&nbsp;</span><span style="color: #FF8000">//&nbsp;This&nbsp;will&nbsp;become&nbsp;'AA'<br /></span><span style="color: #007700">}<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">((array)&nbsp;new&nbsp;</span><span style="color: #0000BB">B</span><span style="color: #007700">());<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

  </div>

  <p class="para">
   The above will appear to have two keys named &#039;AA&#039;, although one of them is
   actually named &#039;\0A\0A&#039;.
  </p>
  
  <p class="para">
   Converting <b><tt>NULL</tt></b> to an <a href="language.types.array.html" class="type array">array</a> results in an empty
   <a href="language.types.array.html" class="type array">array</a>.
  </p>
 </div>

 <div id="language.types.array.comparing" class="sect2">
  <h3 class="title">Comparing</h3>

  <p class="para">
   It is possible to compare arrays with the <a href="function.array-diff.html" class="function">array_diff()</a>
   function and with
   <a href="language.operators.array.html" class="link">array operators</a>.
  </p>
 </div>

 <div id="language.types.array.examples" class="sect2">
  <h3 class="title">Examples</h3>

  <p class="para">
   The array type in PHP is very versatile. Here are some examples:
  </p>

  <div class="informalexample">
   <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;this<br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;array(&nbsp;</span><span style="color: #DD0000">'color'&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #DD0000">'red'</span><span style="color: #007700">,<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'taste'&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #DD0000">'sweet'</span><span style="color: #007700">,<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'shape'&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #DD0000">'round'</span><span style="color: #007700">,<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'name'&nbsp;&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #DD0000">'apple'</span><span style="color: #007700">,<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;key&nbsp;will&nbsp;be&nbsp;0<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;is&nbsp;completely&nbsp;equivalent&nbsp;with<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #DD0000">'color'</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #DD0000">'red'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #DD0000">'taste'</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #DD0000">'sweet'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #DD0000">'shape'</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #DD0000">'round'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #DD0000">'name'</span><span style="color: #007700">]&nbsp;&nbsp;=&nbsp;</span><span style="color: #DD0000">'apple'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$a</span><span style="color: #007700">[]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;=&nbsp;</span><span style="color: #0000BB">4</span><span style="color: #007700">;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;key&nbsp;will&nbsp;be&nbsp;0<br /><br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">[]&nbsp;=&nbsp;</span><span style="color: #DD0000">'a'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">[]&nbsp;=&nbsp;</span><span style="color: #DD0000">'b'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">[]&nbsp;=&nbsp;</span><span style="color: #DD0000">'c'</span><span style="color: #007700">;<br /></span><span style="color: #FF8000">//&nbsp;will&nbsp;result&nbsp;in&nbsp;the&nbsp;array&nbsp;array(0&nbsp;=&gt;&nbsp;'a'&nbsp;,&nbsp;1&nbsp;=&gt;&nbsp;'b'&nbsp;,&nbsp;2&nbsp;=&gt;&nbsp;'c'),<br />//&nbsp;or&nbsp;simply&nbsp;array('a',&nbsp;'b',&nbsp;'c')<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

  </div>

  <div class="example">
   <p><b>Example #1 Using array()</b></p>
   <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">