PHP出现Undefined Offset错误，file_put_contents与explode问题求助

Let's break down what's going wrong here and fix it step by step:

1. Why the "+" isn't splitting your data #

When you pass the rawData parameter via GET, the + character gets automatically decoded as a space by PHP's $_GET superglobal. That means your explode("+", $rawData) is trying to split on spaces instead of the actual + you intended, leaving you with a single array element instead of two. To fix this, you need to either:

• Encode the + as %2B when sending the GET request, or
• Use rawurldecode() on $_GET['data'] to get the original + character back.

2. Why the Undefined Offset error happens #

If $rawData is empty or doesn't contain any +, explode() returns an array with one element. While your loop condition $i < count($lineData) should avoid out-of-bounds access, edge cases (like accidental array modification) or missing GET parameters can still trigger the error. Using a foreach loop instead is safer for array iteration and eliminates this risk entirely.

3. Why your file isn't getting new lines #

You're using " " in your string, which isn't a valid newline escape sequence in PHP. You need to use "\n" (Unix-style newlines) or PHP_EOL (auto-adapts to your server's OS) to get actual line breaks in the output file.

Fixed Code #

Here's the revised code addressing all these issues:

<?php
// Add fallbacks to avoid Undefined Index errors
$fileTitle = $_GET['title'] ?? 'default';
// Decode to preserve the original "+" character
$rawData = rawurldecode($_GET['data'] ?? '');

// Split the data using the correct "+" delimiter
$lineData = explode("+", $rawData);

// Use foreach to safely iterate over the array
foreach ($lineData as $line) {
    // Skip empty lines to avoid blank entries
    if (trim($line) === '') {
        continue;
    }
    
    $txtFileTitle = $fileTitle . ".txt";
    // Use PHP_EOL for proper cross-platform newlines
    $txtFileLineData = $line . PHP_EOL;
    $txtFileStatus = file_put_contents($txtFileTitle, $txtFileLineData, FILE_APPEND);
    
    if ($txtFileStatus !== false) {
        echo "SUCCESS: data written to txt file<br>";
    } else {
        echo "FAIL: could not write to txt file<br>";
    }
}
?>

Key Improvements: #

• Added ?? null coalescing operators to handle missing GET parameters (prevents Undefined Index errors).
• Used rawurldecode() to ensure the + in rawData is preserved for splitting.
• Switched to a foreach loop to eliminate Undefined Offset risks entirely.
• Used PHP_EOL to generate proper line breaks across different operating systems.
• Added a check to skip empty lines, avoiding blank entries if rawData ends with + or has empty segments.

Testing with Your Example #

If you send title=testing and rawData=5000013,0.00,0.00,50.00,0%2B5006529,0.00,0.00,50.00,0 (note %2B instead of +), the code will split the data correctly and write:

5000013,0.00,0.00,50.00,0
5006529,0.00,0.00,50.00,0

to testing.txt.

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