Generate Unique Submission ID in Hidden Field

Description

Generates a human-readable unique ID for each successful form submission and saves it to a designated Hidden field. Supports multiple forms and multiple hidden fields via a config array. Each ID uses a configurable prefix (including any separator) followed by either a random numeric suffix or an ascending numeric suffix.

Usage Notes

  • Form setup: Add a standard Hidden field to each target form in the form editor. Note its field ID. No default value or dynamic population is required.
  • Configuration: Add one array row per form/field pair. For a single ID on one form, use a single row and remove any extra example rows.
  • Required keys per row: form_id, field_id, prefix (string, may be empty), length, sequential. Include start when sequential is true (defaults to 1 if omitted).
  • Prefix: Include any separator in the prefix value (e.g. 'SUB-', 'INV-', or '' for suffix-only output).
  • Random mode (sequential => false): Suffix is a random string of digits only. length is the number of digits (e.g. 8 → 48291037).
  • Sequential mode (sequential => true): Suffix is an ascending number. start is the literal first value assigned (e.g. 62602 with length => 6 → 062602, then 062603, …). length controls zero-padding width on output. Do not use a leading zero in PHP for start (e.g. use 62602, not 062602); padding is applied automatically.
  • Sequential counter: The last assigned value is stored per field in the WordPress options table (gf_unique_submission_id_{form_id}_{field_id}). Changing start after submissions exist has no effect unless the option is deleted manually.
  • Duplicate rows: Each form_id + field_id pair should appear once. Duplicate rows register duplicate hooks and will double-increment or overwrite the same field.
  • Invalid field: If a row references a missing or non-hidden field, that row logs a debug message and is skipped; other rows and the submission continue normally.
  • Concurrent submissions: Sequential mode uses a simple read/increment/write on a WP option — simultaneous submissions could theoretically receive duplicate numbers under heavy load. For high-traffic forms, prefer random mode or add a custom locking strategy.
  • Validation retries: Because the hook runs only after validation passes, a user who fails validation and resubmits gets a new ID on the successful attempt (expected for “per submission”). In sequential mode, failed validations do not consume a number.
  • Save and continue / drafts: ID is assigned on final submission only; draft entries will not have the ID until completion.
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