PHP fix 6/10: Allowed memory size exhausted — stream a CSV instead of loading it all

[vistabylara-dev]

نفاد الذاكرة قد يحدث عندما تُحمَّل ملفات كبيرة دفعة واحدة. المثال يقرأ ملف CSV سطراً بسطر دون الاحتفاظ بكل الصفوف في الذاكرة.

Free code series · Topic 13/50 · PHP fix 6/10

The problem

A PHP import loads an entire CSV and then creates several copies in arrays. Streaming can reduce that particular source of memory pressure. It does not fix every memory leak or an oversized individual row.

Where this belongs in Shopify

PHP runs in an external app, integration service, or server you control. Shopify themes use Liquid, HTML, CSS, and JavaScript; do not paste this PHP into a theme section or Custom Liquid block. If a third-party app owns the failing server, share a sanitized error with that app's support team.

Placement and free suggested code

Save as csv-demo.php. It creates a tiny in-memory fixture for demonstration. In your private background importer, adapt the stream to an approved local file and validate its schema before any writes.

csv-demo.php

<?php
declare(strict_types=1);

$stream = fopen('php://temp', 'w+');
if ($stream === false) {
    throw new RuntimeException('Could not open demo stream.');
}
try {
    fwrite($stream, "sku,quantity\nDEMO-A,2\nDEMO-B,3\n");
    rewind($stream);
    $header = fgetcsv($stream, 0, ',', '"', '');
    if ($header !== ['sku', 'quantity']) {
        throw new RuntimeException('Unexpected CSV header.');
    }
    $count = 0;
    while (($row = fgetcsv($stream, 0, ',', '"', '')) !== false) {
        if (count($row) !== 2) {
            throw new RuntimeException('Unexpected CSV row.');
        }
        // Validate/process one row here; do not accumulate all rows.
        $count++;
    }
    if (!feof($stream)) {
        throw new RuntimeException('CSV read failed.');
    }
    echo 'Rows read: ' . $count . PHP_EOL;
} finally {
    fclose($stream);
}

Verify before using it

The fixture should print Rows read: 2. In staging, test realistic file sizes, malformed rows, and encoding; measure peak memory. This sample validates shape only, not SKU existence or quantity. Establish file and record-size limits because a single huge CSV record can still consume memory.

What was checked for this guide: The demo ran in a PHP WebAssembly CLI runtime. Local fixture checks passed; this is not a test of your host, store, production workflow, or every failure mode.

Precautions and rollback

Do not set memory_limit to unlimited as a blanket fix. A database query buffered before this loop or an accumulated result array can still exhaust memory. For imports, validate rows, use bounded batches and checkpoints, and make retry behavior safe before writing stock or prices.

Back up or commit the existing application before adapting anything. Test on a development copy with dummy data. Restore the previous application version if behavior regresses; reverting code does not undo database writes or external actions. These are educational suggestions, not a universal drop-in repair.

Check the ecommerce workflow

After adapting a fix, verify the affected operation from input to its intended result in your test environment. Check failure handling as well as success. Do not mark a sale or analytics purchase event merely because a PHP script finished. Payment/order state and analytics reporting need their own checks, and repeated requests must not duplicate side effects.

Official references

• PHP manual reference 1
• PHP manual reference 2
• Shopify theme architecture

Share your error and join the free discussion

Comment with the exact error text, PHP version, whether this is your own app or a third-party app, and a short sanitized code sample. Remove passwords, tokens, customer details, and private server paths. What happened just before the error?

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