Hey there! Let's break down the possible issues step by step since your send.php works standalone but the form submission is unresponsive—here are my go-to troubleshooting tips:

Check Basic Form Attributes #

• Verify your <form> tag's action attribute points correctly to send.php—double-check for typos or incorrect relative paths (e.g., if contact.php is in a subfolder, you might need ../send.php instead of just send.php).
• Ensure the form uses the correct method (most likely POST, since that's standard for form submissions). If send.php expects POST data but your form defaults to GET, it won't trigger the email logic.
• Confirm your submit button has type="submit"—a button with type="button" won't trigger form submission unless you add custom JavaScript for it.

Rule Out Frontend JavaScript Interference #

• Open your browser's developer console (F12 → Console tab) and check for any JavaScript errors. A broken script or an accidental event.preventDefault() in a submit listener could block the form from submitting.
• If you're using AJAX to submit the form, inspect the AJAX code: make sure it's targeting the correct send.php path, using the right request method, and handling success/failure callbacks (without feedback, it might look like nothing's happening even if the request is sent).
• Temporarily disable all custom JavaScript on the page and test the form submission—this will quickly tell you if a script is causing the issue.

Check Server-Side & Path Issues #

• Review your server's error logs (e.g., Apache's error.log or Nginx's error.log). Hidden errors like 404s for send.php, permission issues, or PHP fatal errors might be stopping the process without showing anything on the frontend.
• Confirm the file structure matches your form's action path. If your project uses a virtual host, ensure the document root is set correctly so the server can find send.php.

Validate Form Logic #

• Check for frontend form validation: if a required field is missing but the validation message isn't displaying, the form might be blocked from submitting without you noticing. Try temporarily removing validation to test submission.
• In send.php, verify you're properly checking the request method (e.g., if ($_SERVER['REQUEST_METHOD'] !== 'POST')). A miswritten condition here could cause the script to exit early without executing the email code.

Eliminate Environment/Caching Issues #

• Force-refresh the page (Ctrl+F5) and clear your browser cache—stale cached versions of the form can cause unexpected behavior.
• Test the form in an incognito/private window to rule out interference from browser extensions (like ad blockers or script blockers that might block form submissions).

Compare with Your Working Blank Project #

• Line up the form code from your working blank project with contact.php—look for differences in form attributes, hidden fields, or attached event listeners that might be causing the issue.
• Check if your current project includes additional libraries (like Bootstrap or jQuery) that might have default behaviors affecting form submission—sometimes these libraries modify form handling in unexpected ways.

内容的提问来源于stack exchange，提问作者user4285164