Return one node per match from firstChild() - #109

firstChild() broke out of its outer loop as soon as one match had a child element, so it returned at most one node for the whole match set. lastChild() returns one node per match.

$xml = '<?xml version="1.0"?><root><p><i>a</i><i>b</i></p><p><i>c</i><i>d</i></p></root>';

qp($xml, 'p')->firstChild()->textImplode(','); // before: 'a'    after: 'a,c'
qp($xml, 'p')->lastChild()->textImplode(',');  // 'b,d' (unchanged)

Behaviour change: firstChild() now returns the first child element of every match. To get the old result, use firstChild()->first().

Changes

• Drop the $flag and the outer break in QueryFilters::firstChild(), and remove a stale comment
• Update the firstChild() and lastChild() DocBlocks to say they return one child element per match
• Add a CHANGELOG entry

Tests

testFirstChildReturnsOneChildPerMatch matches four elements: one empty, one with only text, one with text before its child elements, and one with a comment before its child element. It fails on main (it gets 'a') and passes with this change. phpunit, lint and lint:min-php all pass.

Fixes #78.

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