Question

please help me in understanding the problem with replacing the child node

$dom = new DOMDocument();
$dom->load('cheat.xml');
$team1sabbr = $dom->getElementsByTagName('team1sabbr');
$textNode = $dom->createTextNode('value-1');
$textNode = $dom->importNode($textNode, true);
$team1sabbr->replaceChild($textNode, $oldNode);
$dom->save('cheat.xml');

its throwing an error like

Fatal error: Call to undefined method DOMNodeList::replaceChild()

cheat.xml looks like

 <?xml version="1.0"?>
<matches>

            <match id="2204">

    <Game></Game> 

        <team1sabbr></team1sabbr> 

        <team2sabbr></team2sabbr>

Answer 1

You need to modify your code to look like the following:

$team1sabbr = $dom->getElementsByTagName('team1sabbr');
$textNode = $dom->createTextNode('value-1');

foreach ($team1sabbr as $team) {
    $team->parentNode->replaceChild($textNode, $team);
}

1. Iterate through each found element
2. Locate the parent of that element
3. Use replaceChild on the parent node.

Edit::
Through comments it seems the question was unclear.

The following is what was required.

$team1sabbr = $dom->getElementsByTagName('team1sabbr');

foreach ($team1sabbr as $team) {
    $team->nodeValue = 'value-1';
}