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<?php function generateTmpFilename(): string { $filename = sys_get_temp_dir().'/'.bin2hex(random_bytes(16)).'.tmp'; touch($filename); return $filename; } $tmpFilename = generateTmpFilename(); $f = fopen($tmpFilename, 'rwb'); # this is the only difference fwrite($f, 'Woop die loop'); fwrite($f, 'Scoop'); fclose($f); # Note that this is empty output var_dump(file_get_contents($tmpFilename)); $tmpFilename = generateTmpFilename(); $f = fopen($tmpFilename, 'wrb'); # this is the only difference fwrite($f, 'I ate'); fwrite($f, 'Noogie'); fclose($f); # And this one contains expected text var_dump(file_get_contents($tmpFilename));

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