PHP查找并修改含POST传入代码的XML文件报错求助

Let's break down why you're seeing those errors and how to fix them:

Root Causes of the Errors #

1. Undefined Offset: 3: Your XPath query $xml->xpath("pedido") returns an array of all <pedido> elements in the XML file. In your example XML, there's only one <pedido> element (so the array has index 0, not 3). Trying to access index 3 when it doesn't exist throws this error.
2. Trying to get property of non-object: When $result[3] doesn't exist, it's not a SimpleXMLElement object—so accessing ->numpedido on a non-object triggers this second error.

Corrected Code #

Here's a revised version of your code that addresses these issues and makes your logic more robust:

// Ensure $dilma is set with the value you're searching for (e.g., from POST)
$dilma = $_POST['numpedido'] ?? ''; // Use null coalescing to avoid undefined variable errors

// Scan the xml directory
$files = scandir('xml/.'); 

foreach ($files as $file) {
    // Skip directory markers
    if ($file === '.' || $file === '..') continue;

    $filePath = "xml/" . $file;
    // Load the XML file and check if it loaded successfully
    $xml = simplexml_load_file($filePath);
    if (!$xml) {
        echo "Failed to load XML file: $filePath<br>";
        continue;
    }

    // Get all pedido elements
    $pedidos = $xml->xpath("pedido");
    // Check if any pedido elements were found
    if (empty($pedidos)) {
        echo "No pedido elements found in $filePath<br>";
        continue;
    }

    // Loop through each pedido to find the matching numpedido
    foreach ($pedidos as $pedido) {
        // Compare the numpedido value (cast to string to avoid type issues)
        if ((string)$pedido->numpedido === (string)$dilma) {
            echo "Found matching pedido in $filePath!<br>";
            // Here you can perform your modification logic
            // Example: Update the status
            $pedido->status = 'Modificado';
            // Save the changes back to the XML file
            $xml->asXML($filePath);
            break; // Exit the loop once found if you only need the first match
        }
    }
}

Key Improvements #

• No hardcoded indexes: Instead of assuming index 3 exists, we loop through all <pedido> elements to find the match.
• XML validation: We check if simplexml_load_file succeeded (in case the XML file is corrupted or invalid).
• Safe variable handling: We use $_POST['numpedido'] ?? '' to ensure $dilma is always defined (even if the POST parameter is missing).
• Type-safe comparison: Casting both values to strings ensures we're comparing content correctly (SimpleXMLElement objects can behave unexpectedly in direct comparisons).
• Modification & saving: Added example code to modify the XML and save the changes back to the file (aligning with your goal of updating the XML).

Notes About Your XML Structure #

In your example XML, there's only one <pedido> element. If your actual files have multiple <pedido> elements nested under a root node (like <pedidos>), adjust your XPath query to $xml->xpath("//pedido") to find all <pedido> elements anywhere in the document.

内容的提问来源于stack exchange，提问作者João Pedro