Hi all,
i've been googling around and found that PHP4 use expat library for xml processing, while in PHP5 expat is removed.. instead it use libxml.
I want to create a script that able to parse xml for both PHP4 and 5. Do I have to write a wrapper class that can seamlessly switch between expat and libxml, according the installed php version? Or should I have to write a pure PHP based xml parser (using regex)?
Which option is better? could you give me any clue on this?
Thank you so much
I'm glad my work doesn't require using all those fancy terms. try this function:
<?php
function xml_read_tags($string,$tag, $nameCase=''){
//this function returns all instances of a given tag in a string, indexed 1-based, with an array structure for all of the attributes. Here is the array structure:
/*----------------------------------------------------------
2004-07-11: added nameCase=1, all attribute names are lcase, 2=all are uppercase
2004-03-20: added flexiblity in the name call, can search for tags via regex, e.g. passing xml_read_tags($string, '((list)|(focus))*Element') will find: 1) listElement, 2)focusElement, and 3) element, another example would be -- t(r)|(head) will find either tr or thead in a table structure.
2004-03-12: added int_strposn (intermediate text position) and int_length (intermediate text length) for ease of use
Array Structure returned:
1 => attribute1 => value1
attribute2 => value2
..
_special => name => tag_name
_special => length => n1
_special => strposn => n2
..
[no other _special keys at this time]
2 => same as instance one
----------------------------------------------------------*/
global $xml_read_tags;
$regex='/<'.$tag.'((\s+[^>]+>)|(>))(.|\s)*$/i';
$masterLength=strlen($string);
$masterString=$string;
while(true){
$fs++;
if($fs>200)break;
ob_start();
$ok=preg_match($regex,$string,$right);
$x=ob_get_contents();
ob_end_clean();
if($x){$xml_read_tags[err]='Parse or other error reading the tag against the string';}
if(!$ok)break;
$i++;
$offsetFromRight=strlen($right[0]);
$offsetFromLeft=$masterLength-$offsetFromRight;
//here is the string
preg_match('/^<'.$tag.'((\s+[^>]+>)|(>))/i',$right[0],$exact);
$this=$exact[0];
$tagLength=strlen($this);
preg_match('/^<'.$tag.'/i',$this,$nm);
$a[$i][_special][name]=str_replace('<','',$nm[0]);
$p1=($a[$i][_special][strposn]=$offsetFromLeft);
$p2=($a[$i][_special][length]=$tagLength);
if(preg_match_all('/[a-z0-9_-]+\s*((=\s*\'[^\']*\')|(=\s*"[^"]*")|(=[^ \/>]+))/i',$this,$attributes)){
$a[$i][_special][attributes]=count($attributes[0]);
//iterate through each attribute = $j
for($j=0;$j<count($attributes[0]);$j++){
#split by =, declare the array
$thisAttribute=$attributes[0][$j];
$label=trim(substr($thisAttribute,0,strpos($thisAttribute,'=')));
$value=substr($thisAttribute,strpos($thisAttribute,'=')+1);
if(preg_match('/^\'(.|\s)*\'$/',$value)){
$value=preg_replace('/^\'/','',$value);
$value=preg_replace('/\'$/','',$value);
}
if(preg_match('/^"(.|\s)*"$/',$value)){
$value=preg_replace('/^"/','',$value);
$value=preg_replace('/"$/','',$value);
}
#set the values in array
$nameCase==1?$label=strtolower($label):'';
$nameCase==2?$label=strtoupper($label):'';
$a[$i][$label]=$value;
}
}
//munch the name value pairs and look for flags like nowrap
$munch = preg_replace('/[a-z0-9_-]+\s*((=\s*\'[^\']*\')|(=\s*"[^"]*")|(=[^ ]+))(\s|(\/>)|>)/i','',$this);
$munch= preg_replace('/<'.$tag.'/i','',$munch);
$munch= preg_replace('/\/*>/','',$munch);
$munchlist=preg_split('/\s+/',trim($munch));
if(count($munchlist)){
foreach($munchlist as $u){
if($u!==''){
$nameCase==1?$u=strtolower($u):'';
$nameCase==2?$u=strtoupper($u):'';
$a[$i][$u]=1;
$a[$i][_special][flags][]=$u;
}
}
}
//redeclare the string from the new position
$string=
($offsetFromRight>$tagLength?substr($string,-($offsetFromRight-strlen($exact[0]))):'');
if(substr($masterString,$p1+$p2-2,1)!=='/'){
//this is a nesting tag, three cases:
#1. we have a nesting tag, with no subnested similar tags
#2. we have a nesting tag with a subnested similar tag
#3. we have no closing tag -- bad XML form
unset($l);
unset($level);
unset($nextString);
$l=1;
$level[$l]=1;
$nextString=$string;
//========================================
while(true){
//fail safe
$fs2++; if($fs2>200)break;
//match an open or close tag downstream
$nextString=substr($string,-(strlen($nextString)-2));
preg_match('/<(\/*)'.$tag.'(.|\s)*$/i',$nextString,$match2);
$l++;
//get the length of the string
$len=strlen($match2[0]);
if(substr($match2[0],1,1)=='/'){
$level[$l]=-1;
}else{
$level[$l]=1;
}
if(array_sum($level)==0){
// the end tag starts $len from the end of the string
$p3=$a[$i][_special][end_strposn]=$masterLength-$len;
#this is risky
$p4=$a[$i][_special][end_length]=strlen($tag)+3;
$p5=$a[$i][_special][total_length]=$a[$i][_special][end_strposn] - $a[$i][_special][strposn]+$a[$i][_special][end_length];
$a[$i][_special][int_strposn]=$p1+$p2;
$a[$i][_special][int_length]=($p3-$p1)-$p2;
break;
}else{
$nextString=substr($nextString, -($len));
}
}
//========================================
}
}
return $a;
}// end xml_read_tags()
?>
You could have a libxml-based class and an expat-based class. Provided they have the same interface you could give them the same name and:
if(extension_loaded('libxml'))
{
include 'libxml_based_parser.php';
}
else
{
include 'expat_based_parser.php';
}But where did you hear that expat had been removed from PHP5?
Oh, and sfullman, you forgot about processing instructions, entity declarations, and namespaces (to name a few 
)
hey weed, it works for me :-) - the xml parser is very basic and realy only deals with HTML tags but it's been a workhorse in my programming. I'd love to get some feedback and improvement on it if I could place it in an article - I've asked and asked about that but never any response from the owners.
thanks though, send me any links on these things I'm missing and I'll look at it
Sam
Weedpacket wrote:You could have a libxml-based class and an expat-based class. Provided they have the same interface you could give them the same name and:
if(extension_loaded('libxml')) { include 'libxml_based_parser.php'; } else { include 'expat_based_parser.php'; }But where did you hear that expat had been removed from PHP5?
Oh, and sfullman, you forgot about processing instructions, entity declarations, and namespaces (to name a few