What is the best way to write a large file to disk in PHP?

I have a PHP script that occasionally needs to write large files to disk. Using file_put_contents(), if the file is large enough (in this case around 2 MB), the PHP script runs out of memory (PHP Fatal error: Allowed memory size of ###开发者_JS百科##### bytes exhausted). I know I could just increase the memory limit, but that doesn't seem like a full solution to me--there has to be a better way, right?

What is the best way to write a large file to disk in PHP?

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You'll need a temporary file in which you put bits of the source file plus what's to be appended:

$sp = fopen('source', 'r');
$op = fopen('tempfile', 'w');

while (!feof($sp)) {
   $buffer = fread($sp, 512);  // use a buffer of 512 bytes
   fwrite($op, $buffer);
}

// append new data
fwrite($op, $new_data);    

// close handles
fclose($op);
fclose($sp);

// make temporary file the new source
rename('tempfile', 'source');

That way, the whole contents of source aren't read into memory. When using cURL, you might omit setting CURLOPT_RETURNTRANSFER and instead, add an output buffer that writes to a temporary file:

function write_temp($buffer) {
     global $handle;
     fwrite($handle, $buffer);
     return '';   // return EMPTY string, so nothing's internally buffered
}

$handle = fopen('tempfile', 'w');
ob_start('write_temp');

$curl_handle = curl_init('http://example.com/');
curl_setopt($curl_handle, CURLOPT_BUFFERSIZE, 512);
curl_exec($curl_handle);

ob_end_clean();
fclose($handle);

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It seems as though I always miss the obvious. As pointed out by Marc, there's CURLOPT_FILE to directly write the response to disk.

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Writing line by line (or packet by packet in case of binary files) using functions like fwrite()

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Try this answer:

    $file   = fopen("file.json", "w");

    $pieces = str_split($content, 1024 * 4);
    foreach ($pieces as $piece) {
        fwrite($file, $piece, strlen($piece));
    }

    fclose($file);