What Characters Are Allowed in PDO Placeholders?

PDO Placeholders: Unveiling Valid Characters

When utilizing PHP with PDO, it's crucial to adhere to specific guidelines regarding placeholders used in prepared statements. While the documentation may seem elusive, the source code provides a definitive answer.

According to the code, PDO placeholders can exclusively consist of alphanumeric characters and underscores. This means that the placeholder ':colour' in the provided example adheres to the convention.

Alternatives to Hyphens

In situations where hyphens are not permitted, it's advisable to explore alternative naming conventions. Consider using underscores or camel casing to achieve a similar semantic effect without invalidating the query.

For instance, instead of ':user-name', use ':user_name' or ':userName'. These alternatives maintain the intended parameter name while complying with the PDO placeholder restrictions.

Comprehensive Character Set

The following regular expression defines the complete set of characters that can be used in PDO placeholders:

BINDCHR = [:][a-zA-Z0-9_]+;

This expression indicates that the placeholder name must start with a colon ':' followed by at least one character (alphanumeric or underscore). The name can be any length.

By adhering to these character guidelines, you can ensure the validity of PDO placeholders and avoid potential query failures.

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