disambiguate semantics of search_value

The definition of `search_value` in "Parameters" is a bit ambiguous. "these values" _could_ be interpreted to mean that if an array is passed as the `$search_value`, keys of elements of `$search_value` that match _any_ of those `$array` elements will be returned.
Note, the "Description" section does not have this ambiguity as it states "that value" instead of "those values".

php/doc-en@8b00eb9

Author: mumumu

reference/array/functions/array-keys.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!-- $Revision$ -->
-<!-- EN-Revision: 05e4c11653efce0a9eaf1dadda67fa42fe58c23d Maintainer: hirokawa Status: ready -->
+<!-- EN-Revision: 8b00eb9807eb2aec3263226eb770a0885ebc804e Maintainer: hirokawa Status: ready -->
 <!-- Credits: mumumu -->
 <refentry xml:id="function.array-keys" xmlns="http://docbook.org/ns/docbook">
  <refnamediv>
@@ -47,7 +47,7 @@
      <term><parameter>search_value</parameter></term>
      <listitem>
       <para>
-       指定した場合は、これらの値を含むキーのみを返します。
+       指定した場合は、この値を含むキーのみを返します。
       </para>
      </listitem>
     </varlistentry>