Say you have a file with a bunch of nice-xml documents inside and you want them all as individual files. I come across this problem quite often so I thought it would be a good idea to have a script here showing how I usually sole this problem (PHP >= 4.3).

<?php
//Check the number of arguments
if($argc != 5){
    echo "Usage: splitxml <filename> <starttag> <endtag> <path>n";
    echo "<filename> - filename of file with xmls inn";
    echo "<starttag> - first tag of the xml you want to extractn";
    echo "<endtag> - last tag of the xml you want to extractn";
    echo "<path> - where you want the files to be created";
    exit();
}

// Read file into an array
$xml = file($argv[1]);

$starttag = $argv[2];
$endtag = $argv[3];
$resultpath = $argv[4];

$tmp = array();
$counter = 0;
$recording = false;

foreach($xml as $row){
    // Found start tag - start "recording"
    if(strpos($row, $starttag) !== false){
        $recording = true;
    }
    // Save all rows if "recording"
    if($recording){
        $tmp[] = $row;
    }
    // Found end tag - stop "recording" and save file
    if(strpos($row, $endtag) !== false){
        $fp = fopen($resultpath.'/file'.$counter++.'.xml', 'w');
        fwrite($fp, implode("",$tmp));
        fclose($fp);
        $tmp = array();
        $recording = false;
    }
}
?>

Here is an example of how the file can look (books.xml):

--------------------
<book>
    <title>Ronja</title>
    <author>Astrid Lindgren</author>
</book>
--------------------
<book>
    <title>Barnen i Bullerbyn</title>
    <author>Astrid Lindgren</author>
</book>
--------------------

To get these book xml into separate files just run the above script with the following parameters:

php splitxml books.xml '' '' books/

This will create the files file0.xml and file1.xml in the directory books/

file0.xml:

<book>
    <title>Ronja</title>
    <author>Astrid Lindgren</author>
</book>

file1.xml:

<book>
    <title>Barnen i Bullerbyn</title>
    <author>Astrid Lindgren</author>
</book>