# How do I evaluate a CQL audience condition from my PHP backend?

Asked by rui.tavares on 2026-10-05. Tags: php, cql, evaluate.

my PHP service picks what to render based on whether the visitor matches an
audience. Right now I fetch a slot for every case and branch on the result, which
feels backwards. I would rather ask "does this visitor match X" once and branch
on that.

Concrete example of what I want: check whether the visitor is a returning user,
or whether they are browsing from Brazil, before deciding the layout. How do I run
a CQL evaluation server-side, and what should I watch out for? A short code shape
would help.

## 2 answers

### Accepted answer from Devon Lane (2026-10-06)

Yeah, evaluate is exactly what you want here. You send a CQL condition and get
back a boolean, so you branch on that instead of fetching a slot per case.

CQL is English-like and case-insensitive, so both of your examples are close to
what you would say out loud:

```cql
user is returning
location's countryName is "br"
```

The one thing to always do is guard the call with a fallback. If the evaluation
fails or times out, you catch it and treat the result as false (or whatever your
safe default is) so a hiccup does not break the request:

```php
$isReturning = false;
try {
    $isReturning = $croct->evaluate('user is returning');
} catch (\Throwable $e) {
    // keep the default
}
```

The [natural vs technical CQL syntax](/answers/cql-natural-vs-technical-syntax)
thread is handy if you want to see the two ways to write the same condition.

### Answer from Priya Raghavan (2026-10-07)

worth adding one behavior that trips people up: undefined variables evaluate to
false by design. so if you reference something that is not set for that visitor,
the condition just comes back false rather than erroring. good for safety, but
it means a typo in an attribute name fails quietly instead of shouting, so
double check names.

also fwiw queries are 1 to 500 characters and target sub-20ms evaluation, so
keeping conditions tight is both faster and easier to read. if you are calling
evaluate on every pageview the [per-pageview evaluate budget](/answers/evaluate-call-per-pageview-budget)
thread is worth a look.

#### Reply from rui.tavares (2026-10-08)

worked. swapped the per-case slot fetches for a couple of evaluate calls
with fallbacks and the branching is way cleaner now. the undefined-to-false
note saved me, had a mistyped attribute