The header('Location: ...') with PHP failed to jump with parameters or lost parameters. The common reasons and solutions are as follows: 1. The URL encoding is incorrect. http_build_query() should be used to automatically handle parameter encoding to avoid manual splicing causing special characters to destroy the URL structure; 2. There is output content before header(), and it is necessary to ensure that there is no output (including spaces, BOM headers, echo, etc.) before calling header(). You can use ob_start() to enable output buffering to temporarily solve it; 3. The browser cache or plug-in interferes with the jump behavior. It is recommended to clear the cache, use incognito mode to test, or add random parameters to the URL to force refresh. Just pay attention to the above three points to effectively solve most jump problems.

When using PHP's header('Location: ...') redirection, if the GET parameter is brought but it cannot jump normally or the parameters are lost, this problem is actually quite common. Usually it is not caused by the grammatical error, but by the improper details.

The URL encoding is incorrect

The most common problem is that the parameters are not coded correctly. If you manually splice the URL but contain special characters (such as spaces, Chinese, &, etc.), it will destroy the URL structure and cause the server to parse it.

?Solution:

• Use http_build_query() to build a query string, which will automatically handle the encoding for you.

 $params = ['name' => 'John Doe', 'city' => 'New York'];
$url = 'target.php?' . http_build_query($params);
header('Location: ' . $url);
exit;

The URL generated in this way is:

 target.php?name=John Doe&city=New York

There will be no garbled or cut-off.

header() has output before

header() function of PHP must be called before any actual content is output, otherwise an error will be reported: "Cannot modify header information - headers already sent".

??Common reasons:

• There is echo , print or var_dump in front of it
• There are blank characters or BOM headers before the beginning of the file
• Contains other files, and that file has output

? Troubleshooting suggestions:

• Check if there are spaces before <?php or line breaks
• Don't have any output before calling header()
• Use ob_start() to enable output buffering to temporarily avoid this problem

Browser cache or plug-in interference

Sometimes you obviously change the code but refresh the page but there is no change. It may be that the browser caches the jump behavior. Especially the 301 jump will be cached for a long time.

? Countermeasures:

• Try clearing the browser cache, or test it in incognito mode
• Use the developer tools to view the Network panel to confirm whether a new request has been executed
• If it is a test environment, you can use different URL parameters to force refresh (for example, add a random number)

 header('Location: target.php?time=' . time());

Although not a long-term solution, it is very useful when debugging.

Summarize the prone to problems

• Not using http_build_query() when splicing URLs results in error in parameter format
• I accidentally outputted the content before header()
• Browser cache makes the jump look "not effective"

These issues are not complicated, but are easily overlooked. As long as you pay attention to the encoding and output order, most cases can be solved.

Basically that's it.

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