<?php
$str = '<img title="Some nice title" border="0" hspace="0" alt="some useful hint" src="http://w...content-available-to-author-only...l.com/somefileprocessor.php/12345/somedir/somesubdir/someniceimage.jpg" width="629" height="464" />';
preg_match_all('/<img[^>]*?\s+src\s*=\s*"([^"]+)"[^>]*?>/i', $str, $matches);
foreach($matches[1] as $match){
echo $match.PHP_EOL;
}
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