archived-doc-en/language/predefined/arrayaccess/offsetexists.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="arrayaccess.offsetexists" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>ArrayAccess::offsetExists</refname>
  <refpurpose>Whether an offset exists</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis role="ArrayAccess">
   <modifier>public</modifier> <type>bool</type><methodname>ArrayAccess::offsetExists</methodname>
   <methodparam><type>mixed</type><parameter>offset</parameter></methodparam>
  </methodsynopsis>
  <para>
   Whether or not an offset exists.
  </para>
  <para>
   This method is executed when using <function>isset</function> or
   <function>empty</function> on objects implementing <classname>ArrayAccess</classname>.
  </para>
  <note>
   <para>
    When using <function>empty</function> <function>ArrayAccess::offsetGet</function> will
    be called and checked if empty only if <function>ArrayAccess::offsetExists</function>
    returns &true;.
   </para>
  </note>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry><term><parameter>offset</parameter></term>
     <listitem>
      <para>
       An offset to check for.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>

 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.success;
  </para>
  <note>
   <para>
    The return value will be casted to <type>bool</type> if non-boolean was returned.
   </para>
  </note>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>ArrayAccess::offsetExists</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
class obj implements ArrayAccess {
    public function offsetSet($offset, $value): void {
        var_dump(__METHOD__);
    }
    public function offsetExists($var): bool {
        var_dump(__METHOD__);
        if ($var == "foobar") {
            return true;
        }
        return false;
    }
    public function offsetUnset($var): void {
        var_dump(__METHOD__);
    }
    #[\ReturnTypeWillChange]
    public function offsetGet($var) {
        var_dump(__METHOD__);
        return "value";
    }
}

$obj = new obj;

echo "Runs obj::offsetExists()\n";
var_dump(isset($obj["foobar"]));

echo "\nRuns obj::offsetExists() and obj::offsetGet()\n";
var_dump(empty($obj["foobar"]));

echo "\nRuns obj::offsetExists(), *not* obj:offsetGet() as there is nothing to get\n";
var_dump(empty($obj["foobaz"]));
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
Runs obj::offsetExists()
string(17) "obj::offsetExists"
bool(true)

Runs obj::offsetExists() and obj::offsetGet()
string(17) "obj::offsetExists"
string(14) "obj::offsetGet"
bool(false)

Runs obj::offsetExists(), *not* obj:offsetGet() as there is nothing to get
string(17) "obj::offsetExists"
bool(true)
]]>
    </screen>
   </example>
  </para>
 </refsect1>


<!--
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><methodname>Classname::Method</methodname></member>
   </simplelist>
  </para>
 </refsect1>
-->

</refentry>
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