ArrayCopyRetainsReferences

warning native off by default

Group: Probable bugs

Copying an array does not detach reference-valued elements. Changing a referenced element through the copy can also change the original array. This inspection is disabled by default because the intended policy or use can vary.

Example

<?php
$a=[1]; $r=&$a[0]; $b=$a; $b[0]=9; echo $a[0];

Reported:

• line 2: Detach referenced array elements before modifying the copy.

Detection

• An explicit reference is bound to a literal-index element of a local array. The array is copied to a distinct local, and that copy writes the same index while the reference remains live. The original element is subsequently read. Require straight-line provenance.
• Resolve builtin functions, classes, constants and methods; user-defined lookalikes are excluded. Follow only bounded local proof in one lexical scope.
• Emit one finding per violating operation, not per supporting evidence statement. When the proof is inconclusive, nothing is reported.

Exceptions (no report)

• Do not report unresolved or shadowed builtin names, unknown values, or incomplete receiver/type provenance. Unknown calls, aliases escaping, and intervening writes invalidate local proof. Similar code outside the stated detection contract is not a finding.
• Both standard suppression forms suppress this native ID.

Fix

None. Choosing a repair requires intent or additional runtime information.

PHP versions

Available throughout supported PHP 5.3–8.5 where the referenced builtin/extension is available. Respect syntax/version-specific receiver contracts; unavailable APIs are not this rule’s concern.

Configure

In custos.json:

{
  "rules": {
    "ArrayCopyRetainsReferences": {
      "enabled": true
    }
  }
}

Suppress

Before the statement or declaration (or the first statement of the file):

// @custos-ignore ArrayCopyRetainsReferences