sqizi

$string = "<item id='1143' type='vendor.model' available='true'><item id='223' type='vendor.model' available='true'><item id='113' type='vendor.model' available='true'>";

function getElvalue($str, $param) {
	
	 preg_match_all("/id='(.*?)'/iu", $str, $outstring);
	
	 for($i=0;$i<count($outstring[1]);$i+=1) {
	  
	     if ( $outstring[1][$i] == $param ) {
			 
			 return 'Я нашёл - действие';
		 }
		 
	 }
}

echo getElvalue($string, '223');