Fix foreach warning in contact form field validate() when value is a string

[agent-sandbox-automattic]

Problem

A PHP warning was being emitted from class-contact-form-field.php:

foreach() argument must be of type array|object, string given

This occurred in the validate() method in two places:

1. The checkbox-multiple case (line 373) — iterates $field_value directly.
2. The image-select case with ismultiple enabled (line 486) — same pattern.

$field_value is built from $_POST[$field_id]. When the POST value is a scalar string (rather than an array), it remains a string after sanitization. The empty() guard only skips the block for falsy values, so a non-empty string reaches the foreach, triggering the warning.

Fix

Cast $field_value to (array) before both foreach loops — consistent with the pattern already used elsewhere in the same file (e.g., foreach ( (array) $this->get_attribute( 'options' ) as … )).

Testing

Added two new unit tests in Contact_Form_Field_Test.php that pass a string $_POST value for checkbox-multiple and image-select (ismultiple) fields and assert that validate() completes without a fatal error or warning, and correctly reports a validation error.

Changelog

projects/packages/forms/changelog/fix-forms-691-foreach-warning-field-validate

Fixes FORMS-691.

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Linear: FORMS-691

This PR was auto-generated by Agent Sandbox. Please review carefully before merging.

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Code Coverage Summary

Cannot generate coverage summary while tests are failing. 🤐

Please fix the tests, or re-run the Code coverage job if it was something being flaky.

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