Why Does My PDO Query Return 0 Rows When the Database Shows a Count?

Having Difficulty Matching Rows in a Database with PDO

When attempting to retrieve the row count for a duplicate email check using PDO, a common issue arises where the database directly provides a count, but PDO's execute() method returns 0. This problem can stem from various causes.

SQL Errors

Firstly, ensure that the query executes without errors. Reference answers on PDO and MySQLi for error handling. Connection errors can also manifest as "no result" errors.

Conditions

Review the conditions in your query. Mutually exclusive conditions, such as WHERE col=1 AND col=2, will prevent any rows from being returned.

Data Issues

Confirm that the variables in your query exist and contain values. Inspect the input data itself for non-printable characters or HTML entities. Use rawurlencode() to identify such characters easily.

Other Concerns

• Database Credentials: Verify that you are connecting to the correct database and that you have proper credentials.
• Character Set/Encoding: Address any character set or encoding issues as outlined in a linked answer.

Troubleshooting Tips

• Enable full error reporting for PDO and PHP to reveal any hidden errors.
• Scrutinize the database data and input data using rawurlencode() to detect any inconsistencies.
• Ensure that the connection credentials are correct and that you are connecting to the intended database.
• Check for character set issues following the checklist provided.

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