fix: preg_replace backreference corruption in preload head injection#7
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getPreloadsHTML() output was passed straight into preg_replace()'s replacement argument. PHP treats $0-$99 in that argument as backreferences regardless of source, so any href containing a literal "$" followed by digits (e.g. a filename like image$1.jpg, or a querystring like ?v=$1) was silently stripped from the injected <link> markup with no error. Switched to preg_replace_callback(), whose return value is used literally.
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Summary
getPreloadsHTML()'s output was passed straight intopreg_replace()'sreplacement argument:
PHP's
preg_replace()treats$0-$99(and\0-\99) in thereplacement string as backreferences regardless of where the string
came from. The pattern here has no capture groups, so any preloaded
href containing a literal
$followed by digits (a filename likeimage$1.jpg, or a querystring like?v=$1) gets that fragmentsilently stripped from the injected
<link>tag — no error, no log,just a broken preload URL.
Verified directly:
Fix: use
preg_replace_callback()instead — its return value is usedliterally and is never re-scanned for backreferences.
Test plan
testDoesNotCorruptHrefsContainingDollarDigitSequencescovering an href of
/img$1.jpg.Test/Unit/Observer/ResponseBeforeTest.phpsuite passes (8/8)against Magento 2.4.8-p3/PHP 8.3.