Read XML file while its being writen into it PHP

Question

Is there a way to read a XML file even the file is broken?

I'm trying to get an XML file while the file is being written into it and output it, but I'm getting an broken error since the root element is not closed because its in the middle of being written.

Is there anyway how to achieve this?

can we ask why you'd want to achieve this? what's wrong with waiting for the file write to be complete then grabbbing? — Ian Wood, Mar 11 '13 at 19:29
Because the file is a big file and it takes a while to be done, I want to output the content before its done. — believe me, Mar 11 '13 at 19:30
what are you using to write to the file? why not use DOMDocument - adding nodes will at least ensure when you are reading the file it will be valid xml... — Ian Wood, Mar 11 '13 at 19:33
@Ian Wood I better use `xmlreader` since its faster and can be divided while writing. — believe me, Mar 11 '13 at 19:40

score 1 · Accepted Answer · answered Mar 11 '13 at 19:34

1

$broken ='<root>
     <item>foo</item>';

$d  = new DOMDocument();
$d->loadXML($broken);
echo $d->saveXML($d); // useless, only prologue
$d->recover = true; // <--  it's limited, but will try its best.
$d->loadXML($broken);
echo $d->saveXML($d);
/*
 * <?xml version="1.0" encoding="UTF-8"?>
 * <root>
 * <item>foo</item></root>
 */

answered Mar 11 '13 at 19:34

Wrikken

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I have to save first the fixed XML file? – believe me Mar 11 '13 at 19:47
If you wish... I only used `->saveXML()` as a method to show whether or not it had recovered as much of the XML as possible or not. You can do whatever you want with the `DOMDocument` after you call `->loadXML()`. – Wrikken Mar 11 '13 at 19:49
Thanks, is it possible to remove the error at the top of the page? – believe me Mar 11 '13 at 19:52
You _could_ set `libxml_use_internal_errors(true);` before you load it, **but I wouldn't recommend it**. I assume this is not a regular occurance, and as ever in production, you set `display_errors` to false, and `log_errors` on, so you'll at least be notified / have logged that your XML is actually broken. – Wrikken Mar 11 '13 at 19:57
I think in my case I have to do it either way, Thanks anyway its awesome. – believe me Mar 11 '13 at 20:00

score 0 · Answer 2 · edited May 23 '17 at 12:28

Either use file locking or make your writes atomic so that other processes don't see half-written files. See the middle of this answer for code for both approaches.

You could also mediate your writes through something that handles the concurrency for you and gives you consistent reads and writes, i.e. a database. It doesn't have to be a full-blown standalone process--you can use sqlite or a simple key-value store.

Read XML file while its being writen into it PHP

2 Answers2