phalcon/cphalcon · error · InvalidCheckExpression

CHECK expression must be a non-empty string

Error message

CHECK expression must be a non-empty string

What it means

Even when definition['expression'] exists, Phalcon\Db\Check rejects values that are not strings or that are the empty string. A CHECK constraint needs a non-empty SQL boolean expression, so integers, nulls, arrays, or '' all throw InvalidCheckExpression at construction time.

Source

Thrown at phalcon/Db/Check.zep:76

     * prefix in that case.
     *
     * @var string
     */
    protected name;

    /**
     * Phalcon\Db\Check constructor
     */
    public function __construct( string name,  array definition)
    {
        var expression;

        if unlikely !fetch expression, definition["expression"] {
            throw new CheckExpressionRequired();
        }

        if unlikely typeof expression != "string" || expression === "" {
            throw new InvalidCheckExpression();
        }

        let this->name       = name;
        let this->expression = expression;
    }

    /**
     * Returns the CHECK expression
     */
    public function getExpression() -> string
    {
        return this->expression;
    }

    /**
     * Returns the constraint name (may be an empty string for unnamed)
     */
    public function getName() -> string

View on GitHub (pinned to b7419de9cd)

Solutions

1. Normalize the expression to a non-empty string: $expr = trim((string) $expr); and reject '' explicitly.
2. Validate external input before building the Check: is_string($expr) && $expr !== ''.
3. Reject constraint config with empty expressions at load time instead of at DDL time.

Example fix

// before
$expr = $config['check'] ?? '';
$check = new Check('chk_price', ['expression' => $expr]); // '' throws InvalidCheckExpression

// after
$expr = trim((string) ($config['check'] ?? ''));
if ($expr === '') {
    throw new InvalidArgumentException('Check expression missing in config');
}
$check = new Check('chk_price', ['expression' => $expr]);

if (!is_string($expr) || $expr === '') {
    throw new InvalidArgumentException('CHECK expression must be a non-empty string');
}
$check = new Check('chk', ['expression' => $expr]);

function isNonEmptyString(mixed $value): bool
{
    return is_string($value) && $value !== '';
}

When it happens

Trigger: new Check('chk', ['expression' => 0]) or ['expression' => null] after a config miss; expressions built by concatenation that yield ''; JSON payloads where a numeric value stays numeric; using the empty string as a 'no constraint' marker.

Common situations: Config-driven constraints where a missing value falls back to '' via ?? ''; API/JSON inputs keeping scalars typed; template concatenation producing empty output; misunderstanding null vs '' semantics (null key absent is a different exception).

Related errors

• CHECK expression is required
• Column generation expression must be a string
• Dropping a CHECK constraint is not supported by SQLite
• DATABASE PARAMETER 'FOREIGN_KEY_CHECKS' HAS TO BE 1
• The table must contain at least one column

AI-assisted analysis of phalcon/cphalcon@b7419de9cd (2026-08-21). Data as JSON: /api/errors/dd3b19c01d73fb30. Report an issue: GitHub.