$re = '/(?:(?!<(?:field|exclGroup)(?!\w)(?>"[\S\s]*?"|\'[\S\s]*?\'|(?:(?!\/>)[^>])?)+>)[\S\s])*(?><(field|exclGroup)(?=(?:[^>"\']|"[^"]*"|\'[^\']*\')*?\sname\s*=\s*(?:([\'"])([\S\s]*?)\2))\s+(?>"[\S\s]*?"|\'[\S\s]*?\'|(?:(?!\/>)[^>])?)+>)(?:(?&core)|)<\/\1\s*>(?:(?!<(?:field|exclGroup)(?!\w)(?>"[\S\s]*?"|\'[\S\s]*?\'|(?:(?!\/>)[^>])?)+>)[\S\s])*(?(DEFINE)(?<core>(?>(?><([\w:]+)(?>"[\S\s]*?"|\'[\S\s]*?\'|(?:(?!\/>)[^>])?)+>)(?:(?&core)|)<\/\5\s*>|(?!<\/[\w:]+\s*>)(?>[\S\s]))+))/';
$str = '<field xmlns="http://www.xfa.org/schema/xfa-template/2.8/" y="0in" x="0.343mm" w="8.881pt" h="9.108pt" name="detcon_recreation_only">
<ui>
<checkButton size="8.881pt">
<border>
<edge stroke="lowered"/>
<fill/>
</border>
</checkButton>
</ui>
<font size="0pt" typeface="Adobe Pi Std"/>
<para vAlign="middle"/>
<value>
<text>0</text>
</value>
<items>
<text>1</text>
<text>0</text>
<text/>
</items>
</field>
<field xmlns="http://www.xfa.org/schema/xfa-template/2.8/" name="detcon_special_housing" y="5.393mm" w="27.94mm" h="4.134mm" x="0.343mm">
<ui>
<choiceList>
<border>
<edge stroke="lowered"/>
</border>
<margin/>
</choiceList>
</ui>
<font typeface="Arial Narrow" size="6pt"/>
<margin topInset="0mm" bottomInset="0mm" leftInset="0mm" rightInset="0mm"/>
<para vAlign="middle"/>
<value>
<text>NA</text>
</value>
<items>
<text>Not Applicable</text>
<text>Hotel Component</text>
</items>
<items save="1" presence="hidden">
<text>NA</text>
<text>HC</text>
</items>
</field>
<exclGroup xmlns="http://www.xfa.org/schema/xfa-template/2.8/" name="detcon_photo_taken" x="0in" y="0in">
<?templateDesigner itemValuesSpecified 1?>
<field w="12.446mm" h="3.825mm" name="lb_yes">
<ui>
<checkButton size="1.7639mm" shape="round">
<border>
<?templateDesigner StyleID apcb1?>
<edge/>
<fill/>
</border>
</checkButton>
</ui>
<font typeface="Myriad Pro"/>
<margin leftInset="1mm" rightInset="1mm"/>
<para vAlign="middle"/>
<caption placement="right" reserve="7.698mm">
<para vAlign="middle" spaceAbove="0pt" spaceBelow="0pt" textIndent="0pt" marginLeft="0pt" marginRight="0pt"/>
<font size="8pt" typeface="Arial Narrow" baselineShift="0pt"/>
<value>
<text>YES</text>
</value>
</caption>
<value>
<text xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>
</value>
<items>
<text>1</text>
</items>
</field>
<field w="28.702mm" h="3.825mm" name="lb_no" x="13.233mm">
<ui>
<checkButton size="1.7639mm" shape="round">
<border>
<?templateDesigner StyleID apcb1?>
<edge/>
<fill/>
</border>
</checkButton>
</ui>
<font typeface="Myriad Pro"/>
<margin leftInset="1mm" rightInset="1mm"/>
<para vAlign="middle"/>
<caption placement="right" reserve="23.954mm">
<para vAlign="middle" spaceAbove="0pt" spaceBelow="0pt" textIndent="0pt" marginLeft="0pt" marginRight="0pt"/>
<font size="8pt" typeface="Arial Narrow" baselineShift="0pt"/>
<value>
<text>NO (see comments)</text>
</value>
</caption>
<value>
<text xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:nil="true"/>
</value>
<items>
<text>0</text>
</items>
</field>
<border>
<edge presence="hidden"/>
</border>
<?templateDesigner expand 1?></exclGroup>';
$subst = "VALUES (12345,\"$3\",\"/Tx\", \"\", \"N\", \"Y\"),\r\n";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php