Quieting PHP 8.2+ deprecated noise from older WP-CLI — three layers to keep JSON parse clean

Our multi-site maintenance tool fires wp plugin list --format=json against the sites it manages. One day, against a specific shared host (Xserver in Japan), this call started failing — and the failure mode was unusually subtle. Both the SSH connection test and the WP-CLI path test ( wp --version ) came back green. Users saw "all diagnostics pass, but the actual operation fails," a frustrating asymmetry. Tracing it back, the root cause was PHP Deprecated warnings emitted by older WP-CLI (2.x) under PHP 8.2+ leaking into the JSON output. This post walks through the three-layer defense we used to structurally absorb the noise without losing real failures. What was happening — Deprecated warnings on stdout The raw output on a problem host looked like this: PHP Deprecated: Creation of dynamic property WP_CLI\Dispatcher\CompositeCommand::$longdesc is deprecated in phar:///usr/bin/wp/vendor/wp-cli/wp-cli/php/... [ {"name":"akismet","status":"active","update":"none", ...}, ... ] Since PHP 8.2, assigning to a dynamic property on a class without #[\AllowDynamicProperties] emits a Deprecated warning. Xserver's /usr/bin/wp (an older WP-CLI 2.x) leans on dynamic properties internally, so running it on PHP 8.2+ produces a steady stream of those warnings. Note: PHP 8.2's dynamic-property deprecation is a healthy direction for the language. But during the transition, you get many libraries that "warn but still work" — WP-CLI was one of them. The actual problem is the host's php.ini : depending on display_errors , those warnings end up on stdout instead of stderr . Calling wp plugin list --format=json returns stdout containing both the warnings and the JSON, and json_decode() fails on the mixed input. Why diagnostics stayed green but operations failed The frustrating asymmetry came from how each test was checking the output: SSH connection test : runs echo ok — passes as long as ok appears somewhere in stdout, extra lines are fine WP-CLI path test : runs wp --version — passes as lon