json_decode(): Argument #1 ($json) must be of type string, int given: what it means and how to fix it

TL;DR: Validate locally, fix the first real error, validate again (no upload).

Troubleshoot json_decode(): Argument #1 ($json) must be of type string, int given quickly and validate JSON locally (no upload).

What the error means

json_decode(): Argument #1 ($json) must be of type string, int given means the parser expected valid JSON but encountered a character/token that cannot appear there. In practice, it usually means the input is not JSON (or not strict JSON), or it is incomplete.

Most common real-world causes

  • The input is not strict JSON (single quotes, comments, trailing commas).
  • The response is truncated (missing closing } / ] / ").
  • The response contains a prefix/suffix (logs, banners, debug output).
  • The payload has invalid escapes or control characters in strings.
  • You are parsing the wrong thing (already-parsed object, HTML, CSV, etc).

Fast debugging steps

  • Validate the JSON as-is to get an exact error location.
  • Check the first and last 50 characters for truncation and prefixes.
  • Fix one issue at a time and re-validate after each change.

Code example (php)

$obj = json_decode($text, true);
if (json_last_error() !== JSON_ERROR_NONE) {
  throw new Exception(json_last_error_msg());
}

Fix without uploading data

If the JSON contains sensitive data, validate and fix it locally. No Upload Tools runs 100% in your browser.

Workflow: validate -> fix the first error -> validate again -> export/convert.

FAQ

Does the exact token matter? Yes. The token often hints at the root cause: < is usually HTML, u is often undefined, and / often points to comments.

Should I just regex-fix JSON? Avoid blind regex edits. Validate after each change so you know what you fixed and what broke.

Privacy & Security
All processing happens locally in your browser. Files are never uploaded.

Next pages to check

Closest crawled pages without impressions yet. Added to speed first-impression conversion.

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Quick fix checklist

  • Reproduce the error on a minimal input.
  • Check type/format and field mapping.
  • Apply the smallest safe fix.
  • Validate on production-like payload.