PHP curl_multi_getcontent Function

last modified April 11, 2025

The PHP curl_multi_getcontent function retrieves content from a cURL handle when used with the multi interface. It's used to fetch response data after executing multiple parallel cURL requests.

Basic Definition

The curl_multi_getcontent function returns the content of a cURL handle if CURLOPT_RETURNTRANSFER was set. It works with the cURL multi interface for parallel requests.

Syntax: curl_multi_getcontent(CurlHandle $handle): ?string. The handle must be part of a multi handle execution. Returns NULL if no content is available or FALSE on failure.

Basic Multiple Requests

This example demonstrates making two parallel requests and getting their contents.

basic_multi.php

<?php

declare(strict_types=1);

$urls = [
    "https://jsonplaceholder.typicode.com/posts/1",
    "https://jsonplaceholder.typicode.com/posts/2"
];

$mh = curl_multi_init();
$handles = [];

foreach ($urls as $url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_multi_add_handle($mh, $ch);
    $handles[] = $ch;
}

$running = null;
do {
    curl_multi_exec($mh, $running);
} while ($running);

foreach ($handles as $ch) {
    $content = curl_multi_getcontent($ch);
    echo $content . "\n";
    curl_multi_remove_handle($mh, $ch);
    curl_close($ch);
}

curl_multi_close($mh);

This code creates two parallel requests to fetch posts. We use curl_multi_exec to process them simultaneously. After execution, we retrieve each response using curl_multi_getcontent. Always clean up handles properly.

Handling Multiple JSON Responses

This example shows how to process multiple JSON responses from parallel requests.

multi_json.php

<?php

declare(strict_types=1);

$userIds = [1, 2, 3];
$mh = curl_multi_init();
$handles = [];

foreach ($userIds as $id) {
    $url = "https://jsonplaceholder.typicode.com/users/{$id}";
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_multi_add_handle($mh, $ch);
    $handles[$id] = $ch;
}

$running = null;
do {
    curl_multi_exec($mh, $running);
} while ($running);

$results = [];
foreach ($handles as $id =>  $ch) {
    $content = curl_multi_getcontent($ch);
    $results[$id] = json_decode($content, true);
    curl_multi_remove_handle($mh, $ch);
    curl_close($ch);
}

curl_multi_close($mh);

print_r($results);

We fetch three user records in parallel. Each response is decoded from JSON and stored in an array. The results maintain association with their original user IDs. This demonstrates efficient batch processing of API data.

Error Handling in Multi Requests

This example demonstrates proper error handling for multiple cURL requests.

multi_error.php

<?php

declare(strict_types=1);

$urls = [
    "https://jsonplaceholder.typicode.com/posts/1",
    "https://invalid.url",
    "https://jsonplaceholder.typicode.com/comments/1"
];

$mh = curl_multi_init();
$handles = [];

foreach ($urls as $i =>  $url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_TIMEOUT, 10);
    curl_multi_add_handle($mh, $ch);
    $handles[$i] = $ch;
}

$running = null;
do {
    curl_multi_exec($mh, $running);
} while ($running);

foreach ($handles as $i =>  $ch) {
    $content = curl_multi_getcontent($ch);
    $error = curl_error($ch);
    
    if ($error) {
        echo "Request {$i} failed: {$error}\n";
    } else {
        echo "Request {$i} succeeded:\n";
        echo substr($content, 0, 100) . "...\n";
    }
    
    curl_multi_remove_handle($mh, $ch);
    curl_close($ch);
}

curl_multi_close($mh);

We process three URLs where one is intentionally invalid. For each request, we check for errors using curl_error. The example shows how to handle both successful and failed requests in a batch operation.

Setting Custom Options for Multi Requests

This example shows how to set different options for each request in a batch.

multi_options.php

<?php

declare(strict_types=1);

$requests = [
    [
        'url' =>  'https://jsonplaceholder.typicode.com/posts/1',
        'method' =>  'GET'
    ],
    [
        'url' =>  'https://jsonplaceholder.typicode.com/posts',
        'method' =>  'POST',
        'data' =>  ['title' =>  'foo', 'body' =>  'bar', 'userId' =>  1]
    ]
];

$mh = curl_multi_init();
$handles = [];

foreach ($requests as $req) {
    $ch = curl_init($req['url']);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    
    if ($req['method'] === 'POST') {
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $req['data']);
    }
    
    curl_multi_add_handle($mh, $ch);
    $handles[] = $ch;
}

$running = null;
do {
    curl_multi_exec($mh, $running);
} while ($running);

foreach ($handles as $i =>  $ch) {
    $content = curl_multi_getcontent($ch);
    echo "Response {$i}:\n";
    echo $content . "\n\n";
    curl_multi_remove_handle($mh, $ch);
    curl_close($ch);
}

curl_multi_close($mh);

We execute both GET and POST requests in parallel. Each handle gets configured with its specific options before being added to the multi handle. This shows the flexibility of the multi interface for different request types.

Processing Large Number of Requests

This example demonstrates handling a large batch of requests efficiently.

large_batch.php

<?php

declare(strict_types=1);

// Generate 10 URLs to fetch
$urls = array_map(
    fn($id) =>  "https://jsonplaceholder.typicode.com/posts/{$id}",
    range(1, 10)
);

$mh = curl_multi_init();
$handles = [];
$results = [];
$concurrency = 5; // Process 5 at a time

foreach ($urls as $i =>  $url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_TIMEOUT, 15);
    curl_multi_add_handle($mh, $ch);
    $handles[$i] = $ch;
    
    // Process in batches to avoid overwhelming the system
    if (count($handles) % $concurrency === 0) {
        $running = null;
        do {
            curl_multi_exec($mh, $running);
        } while ($running);
        
        // Process completed requests
        foreach ($handles as $j =>  $ch) {
            if (curl_getinfo($ch, CURLINFO_HTTP_CODE) === 200) {
                $results[$j] = curl_multi_getcontent($ch);
            }
            curl_multi_remove_handle($mh, $ch);
            curl_close($ch);
        }
        
        $handles = [];
    }
}

// Process any remaining handles
if (!empty($handles)) {
    $running = null;
    do {
        curl_multi_exec($mh, $running);
    } while ($running);
    
    foreach ($handles as $j =>  $ch) {
        if (curl_getinfo($ch, CURLINFO_HTTP_CODE) === 200) {
            $results[$j] = curl_multi_getcontent($ch);
        }
        curl_multi_remove_handle($mh, $ch);
        curl_close($ch);
    }
}

curl_multi_close($mh);

echo "Fetched " . count($results) . " responses\n";

This example processes 10 URLs in batches of 5 for better resource management. We check HTTP status codes before storing results. The approach prevents system overload when dealing with many requests. Results maintain their original order for easy reference.

Best Practices

Batch Size: Limit concurrent requests to avoid system overload.
Error Handling: Check both curl_multi_getcontent and curl_error.
Resource Cleanup: Always remove and close handles properly.
Timeouts: Set CURLOPT_TIMEOUT for each handle.
Memory: Process responses in batches for large operations.

Source

PHP curl_multi_getcontent Documentation

This tutorial covered the PHP curl_multi_getcontent function with practical examples showing its usage for parallel HTTP request processing.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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