The main reasons for header jump failure include early output triggering, variable splicing errors and path configuration problems. 1. Output triggers in advance: Check whether there are echo/print/var_dump or file to introduce empty lines, and use ob_start() to buffer the output; 2. Variable splicing errors: Make sure that the variable has values ??and is formatted correctly, encode parameters with urlencode and print the verification URL; 3. Path or server problems: Confirm the path is correct and the domain name protocol matches, check the .htaccess/Nginx rewrite rules, manually test the URL access permissions and add exit termination script.

Sometimes when using PHP's header('Location: ...') to jump to the page, if the URL contains a variable, the jump does not take effect, or even an error is reported, this is quite common. The main reasons may be that the output is triggered in advance, the path is wrong, or the variable splicing method is incorrect.

The output has been sent, causing the header to fail

This is one of the most common problems. header() function of PHP must be called before anything is output. Even if there is a space, echo or HTML output in front of it, the header setting will fail and an error similar to "headers already sent" will be prompted.

Solution:

• Check whether there are any output statements such as echo , print , var_dump , etc. before header()
• Check if other files (such as config.php) are introduced, which may have empty lines or output
• Use ob_start() to enable output buffering and delay output content

 <?php
ob_start();
// Your logical code header("Location: target.php?id=123");
exit;
?>

Incorrect splicing method

If you are splicing URLs through variables, for example:

 $id = 123;
header("Location: target.php?id=$id");

This writing method itself is fine, but make sure that the variable has values ??and that the spliced ??URL is in the correct format. For example, $id is empty, null or non-number, which may cause incomplete or errors in the jump address.

Suggested practices:

• Print the final URL before jumping to confirm whether the splicing result is correct

 $url = "target.php?id=" . urlencode($id);
// echo $url; // For test, comment out the header("Location: $url");
exit;

• Use urlencode() to encode parameters to avoid problems caused by special characters

Path or server configuration issues

Sometimes the URL to be redirected is written incorrectly, such as the relative path is incorrect, or the absolute path is used but the domain name is written incorrectly, which can also cause the redirect to fail or jump to the error page.

Common Situations:

• The path is written as redirect.php?... , but the actual file name is redirects.php
• http:// was used but the server forced HTTPS, resulting in redirect failure
• The URL rewrite of .htaccess or Nginx configuration affects the jump target

Recommended inspection:

• Print the complete jump URL, copy and paste manually to the browser to see if it can be opened normally
• If deployed on a virtual host, confirm whether you have permission to perform header redirection
• Make sure to use exit; or die(); to terminate subsequent execution of the script

Summarize

When header location fails to jump with variables, first check whether there is any output in advance, then check whether the variable splicing is correct, and finally confirm the jump path and server settings. These issues are relatively basic, but are easy to ignore. Basically, that's all, you can find the reason by typing a few more logs during debugging.

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