PdoFetchIntoRetainsSharedRows

warning native off by default

Group: Probable bugs

Identify array append of an unchanged fetch return in a loop when statement FETCH_INTO mode targets same known object on every fetch. Cloned snapshots and immediate single-row consumption exclude.

Detection

• Report array append of an unchanged fetch return in a loop when statement FETCH_INTO mode targets same known object on every fetch. Cloned snapshots and immediate single-row consumption exclude.
• Resolve builtin functions, classes, constants and methods, including imports and supported named arguments. Follow only bounded local facts within one lexical scope. Receiver and argument provenance must establish the specific API contract; variable names and comments never prove intent.
• The statement is a PDOStatement by its resolved type, or a local variable whose latest write is an unconditional plain assignment of a builtin PDO::query() result. The second form keeps the rule working on targets below PHP 8.0, where PDO::query() carries no native return type.
• The governing setFetchMode() call is the last one on the statement that runs unconditionally before the loop (or whose success guards the loop). It must select PDO::FETCH_INTO with an object target.
• Report one finding per violating operation. A reachable path, unchanged value identity and applicable API behavior are required. Intervening mutation, unknown calls involving tracked values, escaped aliases or exhausted analysis budgets invalidate proof.

Exceptions (no report)

• Exclude unresolved required symbols, user-defined lookalikes, incomplete syntax, unknown required values and unsupported versions.
• No report when another setFetchMode() call on the same statement follows the governing call and either sits on a conditional path before the loop or runs inside the fetch loop or a loop enclosing it: the mode or its target may differ between fetches. Calls after the outermost loop are irrelevant.
• No report when the append is followed, in its own statement list or an enclosing one inside the fetch loop, by an unconditional return, throw, exit or a break that leaves the fetch loop: at most one row is retained, so nothing is shared. A break that only leaves an inner loop or a switch does not count, and neither does a conditional exit.
• Both @custos-ignore PdoFetchIntoRetainsSharedRows and @noinspection PdoFetchIntoRetainsSharedRows suppress this native rule.

Fix

None. A repair requires a semantic decision or application error-handling policy.

PHP versions

Available in PHP 5.3–8.5 where the referenced API exists. Do not apply extension contracts when the resolved API is unavailable. Gate syntax and version-specific behavior to the configured target.

Configure

In custos.json:

{
  "rules": {
    "PdoFetchIntoRetainsSharedRows": {
      "enabled": true
    }
  }
}

Suppress

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

// @custos-ignore PdoFetchIntoRetainsSharedRows